ci: downgrade runner to ubuntu-22.04 and enable full features

Revert the GitHub Actions runner to ubuntu-22.04 for better compatibility and ensure the "full" feature set is passed to cargo-dist during the build process.

.github/workflows/actions-security.yml

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
@@ -56,11 +56,11 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
       - name: Run zizmor
-        uses: zizmorcore/zizmor-action@5f14fd08f7cf1cb1609c1e344975f152c7ee938d # v0.5.6
+        uses: zizmorcore/zizmor-action@192e21d79ab29983730a13d1382995c2307fbcaa # v0.5.7
         with:
           persona: regular

.github/workflows/ci.yml

@@ -24,12 +24,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
       - name: Install Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1
+        uses: actions-rust-lang/setup-rust-toolchain@166cdcfd11aee3cb47222f9ddb555ce30ddb9659 # v1
         with:
           components: rustfmt
           cache-key: fmt
@@ -44,12 +44,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
       - name: Install Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1
+        uses: actions-rust-lang/setup-rust-toolchain@166cdcfd11aee3cb47222f9ddb555ce30ddb9659 # v1
         with:
           components: clippy
           cache-key: clippy
@@ -79,12 +79,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
       - name: Install Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1
+        uses: actions-rust-lang/setup-rust-toolchain@166cdcfd11aee3cb47222f9ddb555ce30ddb9659 # v1
         with:
           cache-key: check
 
@@ -102,12 +102,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
       - name: Install Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1
+        uses: actions-rust-lang/setup-rust-toolchain@166cdcfd11aee3cb47222f9ddb555ce30ddb9659 # v1
         with:
           cache-key: test
 
@@ -136,12 +136,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
       - name: Install Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1
+        uses: actions-rust-lang/setup-rust-toolchain@166cdcfd11aee3cb47222f9ddb555ce30ddb9659 # v1
         with:
           cache-key: docs
 

.github/workflows/interop-netem.yml

@@ -25,12 +25,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
       - name: Install Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1
+        uses: actions-rust-lang/setup-rust-toolchain@166cdcfd11aee3cb47222f9ddb555ce30ddb9659 # v1
         with:
           cache-key: interop-netem
 

.github/workflows/rust-clippy.yml

@@ -24,12 +24,12 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
       - name: Install Rust toolchain
-        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1
+        uses: actions-rust-lang/setup-rust-toolchain@166cdcfd11aee3cb47222f9ddb555ce30ddb9659 # v1
         with:
           components: clippy
           cache-key: clippy-sarif
@@ -60,7 +60,7 @@ jobs:
           exit 0
 
       - name: Upload Clippy SARIF
-        uses: github/codeql-action/upload-sarif@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4
+        uses: github/codeql-action/upload-sarif@54f647b7e1bb85c95cddabcd46b0c578ec92bc1a # v4
         if: always()
         with:
           sarif_file: rust-clippy-results.sarif

.github/workflows/semver.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 

.github/workflows/supply-chain.yml

@@ -38,7 +38,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 
@@ -56,7 +56,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
         with:
           persist-credentials: false
 

Cargo.toml

@@ -10,15 +10,15 @@ resolver = "2"
 [workspace.package]
 edition = "2021"
 license = "Apache-2.0"
-rust-version = "1.75"
+rust-version = "1.85"
 repository = "https://github.com/Lochnair/irtt-rs"
 homepage = "https://github.com/Lochnair/irtt-rs"
 readme = "README.md"
 
 [workspace.dependencies]
-irtt-proto = { version = "0.3.0", path = "crates/irtt-proto" }
-irtt-client = { version = "0.3.0", path = "crates/irtt-client" }
-irtt-stats = { version = "0.3.0", path = "crates/irtt-stats" }
+irtt-proto = { version = "0.4.0", path = "crates/irtt-proto" }
+irtt-client = { version = "0.4.0", path = "crates/irtt-client" }
+irtt-stats = { version = "0.4.0", path = "crates/irtt-stats" }
 
 [profile.release]
 opt-level = "z"

README.md

@@ -15,7 +15,7 @@ This repository currently provides:
 - `irtt-tui`, an optional terminal UI applet when built with the `tui` feature
 - `irtt-client`, a Rust library for running client sessions and consuming events
 - finite and continuous probe runs
-- human, simple, machine-readable, and RTT-only stream output modes
+- table, CSV, TSV, and JSON Lines event-row output formats with selectable columns
 - optional local summary statistics
 
 Server support is not implemented.
@@ -24,7 +24,7 @@ confusing overlap with upstream IRTT.
 
 ## Install
 
-Requires Rust 1.75 or newer.
+Requires Rust 1.85 or newer.
 
 From a local checkout:
 
@@ -44,13 +44,37 @@ cargo install --path crates/irtt-cli --features tui
 Or run it directly without installing:
 
 ```sh
-cargo run -p irtt-cli -- <server>
+cargo run -p irtt-cli --bin irtt-cli -- <server>
 ```
 
 For space-sensitive packaging, such as OpenWrt packages, distributors can ship
-only `irtt-rs` and symlink or hardlink applet names such as `irtt-cli`,
-`irtt-tui`, and future server applet names to it. Applet dispatch is based on
-the invoked binary name.
+only `irtt-rs` and symlink or hardlink enabled applet names such as `irtt-cli`
+and, when built with the `tui` feature, `irtt-tui` to it. Applet dispatch is
+based on the invoked binary name. Server support is not implemented.
+
+cargo-dist release archives are currently configured with the `full` feature
+set, so target archives bundle the enabled applet binaries: `irtt-rs`,
+`irtt-cli`, and `irtt-tui`. That is separate from space-sensitive package
+layouts, which may still ship one dispatcher binary plus applet-name symlinks
+or hardlinks. cargo-dist is not currently configured to create those links.
+
+## Build verification
+
+Useful local release/package sanity checks:
+
+```sh
+cargo fmt --check
+cargo test -p irtt-cli
+cargo clippy --workspace --all-targets -- -D warnings
+cargo build -p irtt-cli --release
+cargo build -p irtt-cli --no-default-features --release
+cargo build -p irtt-cli --features tui --release
+cargo build -p irtt-cli --all-features --release
+```
+
+The no-default-features build only provides the `irtt-rs` dispatcher binary;
+the default build provides `irtt-rs` and `irtt-cli`; `tui`, `full`, and
+all-features builds also provide `irtt-tui`.
 
 ## CLI usage
 
@@ -72,13 +96,29 @@ Run continuously:
 irtt-cli <server> --duration 0
 ```
 
-Use a specific output mode:
+Probe multiple targets concurrently:
 
 ```sh
-irtt-cli <server> --output human
-irtt-cli <server> --output simple
-irtt-cli <server> --output machine
-irtt-cli <server> --output rtt-us
+irtt-cli host-a:2112 host-b:2112
+irtt-cli --target ams=ams.example.com:2112 --target sg=sg.example.com:2112
+irtt-cli host-a:2112 host-b:2112 --pacing burst
+```
+
+For positional multi-target runs, the original target string is used as the
+logical target label. Repeated positional strings get a stable numeric suffix.
+For `--target label=host:port`, `label` is used in the `target` output column.
+Labels must be unique. `--pacing staggered|burst` selects managed group pacing
+for multi-target runs; the default is `staggered`.
+
+Use a specific output format or column selection:
+
+```sh
+irtt-cli <server> --format table
+irtt-cli <server> --format jsonl
+irtt-cli <server> --format csv --columns event,seq,remote,effective_rtt_us
+irtt-cli host-a:2112 host-b:2112 --format csv --columns target,seq,effective_rtt_us
+irtt-cli <server> --format tsv --columns effective_rtt_us --header never
+irtt-cli --list-columns
 ```
 
 With the optional TUI feature, `irtt-tui` opens a live cumulative dashboard for
@@ -89,6 +129,8 @@ session gracefully.
 ```sh
 irtt-tui <server>
 irtt-tui <server> --duration 30s
+irtt-tui host-a:2112 host-b:2112 --pacing burst
+irtt-tui --target ams=ams.example.com:2112 --target sg=sg.example.com:2112
 cargo run -p irtt-cli --features tui --bin irtt-tui -- <server>
 ```
 
@@ -96,37 +138,81 @@ For available options:
 
 ```sh
 irtt-cli --help
-irtt-tui --help
+irtt-tui --help   # when built or installed with the tui feature
 ```
 
-## Machine output
+## Event row output
 
-Use `--output machine` for line-oriented `key=value` output intended for scripts, monitoring, and autorate consumers.
+The stream client separates event row rendering from final summaries. Event rows
+are controlled by `--format`, `--columns`, and `--header`; final summaries remain
+separate table-style text and are printed for table output when the run policy
+allows a summary.
+
+Formats:
+
+- `table`: default, terminal-readable columns with a header
+- `csv`: comma-separated rows, intended for scripts
+- `tsv`: tab-separated rows, useful for one-value streams and shell pipelines
+- `jsonl`: one JSON object per event row, suitable for streaming consumers
+
+Headers are controlled with `--header auto|always|never`. In `auto`, table, CSV,
+and TSV print one header row; JSON Lines never prints a header.
+
+Columns are selected with `-c, --columns <COLUMNS>`, where `COLUMNS` is a
+comma-separated list. Use `--list-columns` to print the available names. Useful
+columns include:
+
+```text
+target, event, seq, remote, token, rtt, rtt_us, raw_rtt_us, effective_rtt_us,
+adjusted_rtt_us, rd, rd_us, sd, sd_us, ipdv, ipdv_us, proc,
+server_processing_us, bytes, send_call_us, timer_error_us, highest_seen,
+server_received, server_window, dscp, ecn, traffic_class, kernel_rx_ns,
+warning_kind, message, event_wall_ns, client_send_wall_ns,
+client_receive_wall_ns
+```
+
+Aliases are accepted for readability: `receive_delay` and `receive_delay_us`
+for `rd` and `rd_us`, `send_delay` and `send_delay_us` for `sd` and `sd_us`,
+`server_processing` for `proc`, `server_received_count` for
+`server_received`, and `server_received_window` for `server_window`.
+
+The default single-target table output favors readability with compact columns:
+`event,seq,rtt,rd,sd,ipdv,proc,message`. It omits `echo_sent` rows. Passing
+`--columns default` is the same as omitting `--columns`, including the default
+table row filtering. Multi-target defaults add `target` as the first column so
+rows can be attributed to a logical target label. Custom table column selections
+include all event rows. CSV, TSV, and JSONL default to all non-target columns
+for single-target export and include `target` by default for multi-target
+export; use `--columns all` explicitly to request every column in any format.
+Missing table values render as `-`; missing CSV and TSV values render as empty
+fields; missing JSONL values render as `null`.
+
+Use JSON Lines for structured event streaming:
 
 Example:
 
 ```sh
-irtt-cli <server> --duration 0 --interval 250ms --output machine
+irtt-cli <server> --duration 0 --interval 250ms --format jsonl
 ```
 
-Each line represents one client event and starts with an `event` field, for example:
+Each line is one client event object, for example:
 
-```text
-event=echo_reply seq=4 remote=203.0.113.10:2112 client_send_wall_ns=1760000000000000000 client_receive_wall_ns=1760000000012400000 raw_rtt_us=12400 effective_rtt_us=12100 adjusted_rtt_us=12100 server_receive_wall_ns=1760000000006100000 server_receive_mono_ns=5000006100000 server_send_wall_ns=1760000000006400000 server_send_mono_ns=5000006400000 server_processing_us=300 client_to_server_us=6100 server_to_client_us=6000 server_received_count=5 server_received_window=0x1f dscp=0 ecn=0 kernel_rx_ns=none
+```json
+{"event":"echo_reply","seq":4,"remote":"203.0.113.10:2112","token":null,"rtt":"12.1ms","rtt_us":12100,"raw_rtt_us":12400,"effective_rtt_us":12100,"adjusted_rtt_us":12100,"rd":"6.0ms","rd_us":6000,"sd":"6.1ms","sd_us":6100,"ipdv":"300.0µs","ipdv_us":300,"proc":"300.0µs","server_processing_us":300,"bytes":64,"send_call_us":null,"timer_error_us":null,"highest_seen":null,"server_received":5,"server_window":"0x1f","dscp":0,"ecn":0,"traffic_class":0,"kernel_rx_ns":null,"warning_kind":null,"message":null,"event_wall_ns":1760000000012400000,"client_send_wall_ns":1760000000000000000,"client_receive_wall_ns":1760000000012400000}
 ```
 
-Consumers should match on `event=...` and read the fields they need. Unknown fields should be ignored.
-RTT fields are reported in microseconds. `raw_rtt_us` is the measured client
-send-to-receive RTT. `effective_rtt_us` and `adjusted_rtt_us` are signed and may
-be negative when server processing exceeds the raw RTT or timing correction
-produces a negative adjusted value. When one-way delay fields are present,
-`client_to_server_us` and `server_to_client_us` are also signed microseconds and
-may be negative due to wall-clock skew.
+Consumers should match on the `event` property and read the columns they need.
+RTT, send-call, and timer-error `*_us` fields are reported in microseconds.
+`raw_rtt_us` is the measured client send-to-receive RTT. `effective_rtt_us` and
+`adjusted_rtt_us` are signed and may be negative when server processing exceeds
+the raw RTT or timing correction produces a negative adjusted value. When
+one-way delay fields are present, `sd_us` and `rd_us` are also signed
+microseconds and may be negative due to wall-clock skew.
 
-For consumers that only need RTT values, use:
+For consumers that only need effective RTT values in microseconds, use:
 
 ```sh
-irtt-cli <server> --output rtt-us
+irtt-cli <server> --format tsv --columns effective_rtt_us --header never
 ```
 
 ## Library usage

crates/irtt-cli/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-cli"
-version = "0.3.0"
+version = "0.4.0"
 description = "Command-line IRTT-compatible client"
 edition.workspace = true
 license.workspace = true
@@ -16,29 +16,31 @@ doc = false
 
 [[bin]]
 name = "irtt-rs"
-path = "src/main.rs"
+path = "src/bin/irtt-rs.rs"
 
 [[bin]]
 name = "irtt-cli"
-path = "src/main.rs"
+path = "src/bin/irtt-cli.rs"
 required-features = ["client"]
 
 [[bin]]
 name = "irtt-tui"
-path = "src/main.rs"
+path = "src/bin/irtt-tui.rs"
 required-features = ["tui"]
 
 [features]
 default = ["client", "stats"]
-client = ["dep:irtt-client", "dep:irtt-proto"]
-stats = ["client", "dep:irtt-stats"]
-tui = ["client", "stats", "dep:ratatui", "dep:crossterm"]
+client-runtime = ["dep:irtt-client", "dep:irtt-proto"]
+client = ["client-runtime"]
+stats = ["client-runtime", "dep:irtt-stats"]
+tui = ["client-runtime", "stats", "dep:ratatui", "dep:crossterm"]
+full = ["client", "stats", "tui"]
 
 [dependencies]
 clap = { version = "4.6.1", features = ["derive"] }
-crossterm = { version = "0.28.1", optional = true }
+crossterm = { version = "0.29.0", optional = true }
 ctrlc = "3.5.2"
 irtt-client = { workspace = true, optional = true }
 irtt-proto = { workspace = true, optional = true }
 irtt-stats = { workspace = true, optional = true }
-ratatui = { version = "0.29.0", optional = true }
+ratatui = { version = "0.30.2", optional = true }

crates/irtt-cli/src/applet.rs

@@ -1,4 +1,6 @@
-use std::path::Path;
+use std::{ffi::OsString, path::Path};
+
+use clap::Command;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum RequestedApplet {
@@ -7,20 +9,17 @@ pub enum RequestedApplet {
     Server,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum AppletAvailability {
-    Client,
-    Tui,
-    Server,
-    None,
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum AppletDispatch {
+    Run {
+        applet: RequestedApplet,
+        argv: Vec<OsString>,
+    },
+    Help(String),
 }
 
 pub fn detect_applet_from_argv0(argv0: &str) -> Option<RequestedApplet> {
-    match Path::new(argv0)
-        .file_name()
-        .and_then(|name| name.to_str())
-        .unwrap_or(argv0)
-    {
+    match applet_basename(argv0) {
         "irtt-cli" => Some(RequestedApplet::Client),
         "irtt-tui" => Some(RequestedApplet::Tui),
         "irttd" | "irtt-server" => Some(RequestedApplet::Server),
@@ -29,20 +28,110 @@ pub fn detect_applet_from_argv0(argv0: &str) -> Option<RequestedApplet> {
     }
 }
 
-pub const fn default_applet_for_features(
-    client_enabled: bool,
-    tui_enabled: bool,
-    server_enabled: bool,
-) -> AppletAvailability {
-    if client_enabled {
-        AppletAvailability::Client
-    } else if tui_enabled {
-        AppletAvailability::Tui
-    } else if server_enabled {
-        AppletAvailability::Server
-    } else {
-        AppletAvailability::None
+pub fn dispatch_from_argv(argv: Vec<OsString>) -> Result<AppletDispatch, String> {
+    let argv0 = argv
+        .first()
+        .and_then(|arg| arg.to_str())
+        .unwrap_or("irtt-rs");
+
+    if let Some(applet) = detect_applet_from_argv0(argv0) {
+        return Ok(AppletDispatch::Run { applet, argv });
     }
+
+    let basename = applet_basename(argv0);
+    if basename.starts_with("irtt-") && basename != "irtt-rs" {
+        return Err(format!(
+            "unknown applet name '{basename}'. Known applet names: {}",
+            known_applet_binary_names()
+        ));
+    }
+
+    let Some(command) = argv.get(1).and_then(|arg| arg.to_str()) else {
+        return Err(format!(
+            "choose an applet: {}\n\n{}",
+            applet_command_names(),
+            dispatcher_help()
+        ));
+    };
+
+    match command {
+        "-h" | "--help" => Ok(AppletDispatch::Help(dispatcher_help())),
+        "client" => Ok(AppletDispatch::Run {
+            applet: RequestedApplet::Client,
+            argv: applet_argv("irtt-cli", &argv[2..]),
+        }),
+        "tui" => Ok(AppletDispatch::Run {
+            applet: RequestedApplet::Tui,
+            argv: applet_argv("irtt-tui", &argv[2..]),
+        }),
+        "server" => Ok(AppletDispatch::Run {
+            applet: RequestedApplet::Server,
+            argv: applet_argv("irtt-server", &argv[2..]),
+        }),
+        _ => Err(format!(
+            "unknown applet '{command}'. Choose one of: {}\n\n{}",
+            applet_command_names(),
+            dispatcher_help()
+        )),
+    }
+}
+
+pub fn dispatcher_help() -> String {
+    let mut command = Command::new("irtt-rs")
+        .about("IRTT-compatible multi-applet dispatcher")
+        .subcommand(Command::new("client").about(client_applet_about()))
+        .subcommand(Command::new("tui").about(tui_applet_about()))
+        .subcommand(Command::new("server").about("Server applet is not available in this build"))
+        .after_help(dispatcher_after_help());
+    command.render_help().to_string()
+}
+
+fn client_applet_about() -> &'static str {
+    if cfg!(feature = "client") {
+        "Run the stream client applet"
+    } else {
+        "Stream client applet is not available in this build"
+    }
+}
+
+fn tui_applet_about() -> &'static str {
+    if cfg!(feature = "tui") {
+        "Run the terminal UI applet"
+    } else {
+        "Terminal UI applet is not available in this build"
+    }
+}
+
+fn known_applet_binary_names() -> &'static str {
+    "irtt-rs, irtt-cli, irtt-tui, irtt-server"
+}
+
+fn applet_command_names() -> &'static str {
+    "client, tui, or server"
+}
+
+fn dispatcher_after_help() -> &'static str {
+    if cfg!(feature = "tui") {
+        "Recognized applet binary names: irtt-cli, irtt-tui, irtt-server"
+    } else if cfg!(feature = "client") {
+        "Recognized applet binary names: irtt-cli, irtt-tui, irtt-server\nOptional applet: irtt-tui requires the tui feature"
+    } else {
+        "Recognized applet binary names: irtt-cli, irtt-tui, irtt-server\nOptional applets: irtt-cli requires the client feature; irtt-tui requires the tui feature"
+    }
+}
+
+fn applet_basename(argv0: &str) -> &str {
+    Path::new(argv0)
+        .file_name()
+        .and_then(|name| name.to_str())
+        .unwrap_or(argv0)
+}
+
+fn applet_argv(applet_name: &str, args: &[OsString]) -> Vec<OsString> {
+    let mut argv = Vec::with_capacity(args.len() + 1);
+    argv.push(OsString::from(applet_name));
+    argv.extend(args.iter().cloned());
+    argv
 }
 
 #[cfg(test)]
@@ -68,18 +157,66 @@ mod tests {
     }
 
     #[test]
-    fn default_applet_prefers_client_then_tui() {
+    fn canonical_help_renders_dispatcher_help() {
+        let dispatch = dispatch_from_argv(vec!["irtt-rs".into(), "--help".into()]).unwrap();
+        let AppletDispatch::Help(help) = dispatch else {
+            panic!("expected dispatcher help");
+        };
+        assert!(help.contains("IRTT-compatible multi-applet dispatcher"));
+        assert!(help.contains("client"));
+        if cfg!(feature = "tui") {
+            assert!(help.contains("Run the terminal UI applet"));
+        } else {
+            assert!(help.contains("Terminal UI applet is not available in this build"));
+        }
+        assert!(help.contains("server"));
+    }
+
+    #[test]
+    fn canonical_without_applet_is_an_error() {
+        let err = dispatch_from_argv(vec!["irtt-rs".into()]).unwrap_err();
+        assert!(err.contains("choose an applet"));
+        assert!(err.contains("client"));
+        if cfg!(feature = "tui") {
+            assert!(err.contains("tui"));
+        }
+        assert!(err.contains("server"));
+    }
+
+    #[test]
+    fn canonical_subcommands_dispatch_to_applet_argv() {
         assert_eq!(
-            default_applet_for_features(true, true, false),
-            AppletAvailability::Client
+            dispatch_from_argv(vec!["irtt-rs".into(), "client".into(), "host:2112".into()])
+                .unwrap(),
+            AppletDispatch::Run {
+                applet: RequestedApplet::Client,
+                argv: vec!["irtt-cli".into(), "host:2112".into()],
+            }
         );
         assert_eq!(
-            default_applet_for_features(false, true, false),
-            AppletAvailability::Tui
+            dispatch_from_argv(vec!["irtt-rs".into(), "tui".into(), "host:2112".into()]).unwrap(),
+            AppletDispatch::Run {
+                applet: RequestedApplet::Tui,
+                argv: vec!["irtt-tui".into(), "host:2112".into()],
+            }
         );
         assert_eq!(
-            default_applet_for_features(false, false, false),
-            AppletAvailability::None
+            dispatch_from_argv(vec!["irtt-rs".into(), "server".into()]).unwrap(),
+            AppletDispatch::Run {
+                applet: RequestedApplet::Server,
+                argv: vec!["irtt-server".into()],
+            }
         );
     }
+
+    #[test]
+    fn unknown_irtt_binary_name_is_an_error() {
+        let err = dispatch_from_argv(vec!["/usr/bin/irtt-typo".into()]).unwrap_err();
+        assert!(err.contains("unknown applet name 'irtt-typo'"));
+        assert!(err.contains("irtt-cli"));
+        if cfg!(feature = "tui") {
+            assert!(err.contains("irtt-tui"));
+        }
+        assert!(err.contains("irtt-server"));
+    }
 }

crates/irtt-cli/src/bin/irtt-cli.rs

@@ -0,0 +1,5 @@
+use std::process::ExitCode;
+
+fn main() -> ExitCode {
+    irtt_cli::entry::main()
+}

crates/irtt-cli/src/bin/irtt-rs.rs

@@ -0,0 +1,5 @@
+use std::process::ExitCode;
+
+fn main() -> ExitCode {
+    irtt_cli::entry::main()
+}

crates/irtt-cli/src/bin/irtt-tui.rs

@@ -0,0 +1,5 @@
+use std::process::ExitCode;
+
+fn main() -> ExitCode {
+    irtt_cli::entry::main()
+}

crates/irtt-cli/src/cmd/client/args.rs

@@ -3,15 +3,41 @@ use std::time::Duration;
 use clap::{Parser, ValueEnum};
 use irtt_client::ClientConfig;
 
-use crate::shared::client::{parse_test_duration, CommonClientArgs, TimestampArg};
+use crate::shared::client::{
+    parse_labelled_target, parse_test_duration, resolved_managed_targets, target_specs,
+    CommonClientArgs, GroupPacingArg, LabelledTargetArg, ResolvedTarget, TargetSpec, TimestampArg,
+};
 
 pub const DEFAULT_CLIENT_DURATION: Duration = Duration::from_secs(10);
 
 #[derive(Debug, Clone, Parser)]
 #[command(name = "irtt-cli", about = "Minimal IRTT-compatible stream client")]
 pub struct ClientArgs {
-    /// Server address or host, with optional port.
-    pub server: String,
+    /// Server address or host, with optional port. Repeat for multi-target mode.
+    #[arg(
+        value_name = "TARGET",
+        num_args = 0..,
+        long_help = "Server address or host, with optional port. Repeat the positional target for multi-target mode, for example: irtt-cli host-a:2112 host-b:2112."
+    )]
+    pub targets: Vec<String>,
+
+    /// Explicit labelled target, as label=host:port. Repeat for multi-target mode.
+    #[arg(
+        long = "target",
+        value_name = "LABEL=TARGET",
+        value_parser = parse_labelled_target,
+        long_help = "Explicit labelled target, as label=host:port. Repeat for multi-target mode. The label is used as the target column and must be unique."
+    )]
+    pub labelled_targets: Vec<LabelledTargetArg>,
+
+    /// Managed group pacing for multi-target mode.
+    #[arg(
+        long,
+        value_enum,
+        default_value_t = GroupPacingArg::Staggered,
+        long_help = "Managed group pacing for multi-target mode.\n\nstaggered spaces active targets across the probe interval. burst sends one probe to every active target back-to-back once per interval."
+    )]
+    pub pacing: GroupPacingArg,
 
     #[arg(
         long,
@@ -25,18 +51,52 @@ pub struct ClientArgs {
     #[command(flatten)]
     pub common: CommonClientArgs,
 
-    /// Output format.
-    #[arg(long, value_enum, default_value_t = OutputMode::Human)]
-    pub output: OutputMode,
+    /// Event row output format.
+    #[arg(
+        long,
+        value_enum,
+        default_value_t = OutputFormat::Table,
+        long_help = "Event row output format.\n\nTable is the default interactive format. CSV, TSV, and JSON Lines default to all columns for structured export."
+    )]
+    pub format: OutputFormat,
 
-    /// Include extra fields in human output.
+    /// Comma-separated event row columns, or default/all.
+    #[arg(
+        short = 'c',
+        long,
+        value_name = "COLUMNS",
+        long_help = "Comma-separated event row columns, or default/all.\n\nThe default table columns are compact and hide echo_sent rows. Custom table columns include all event rows. Run --list-columns to see valid names."
+    )]
+    pub columns: Option<String>,
+
+    /// List available event row columns and aliases, then exit.
+    #[arg(
+        long,
+        long_help = "List available event row columns and aliases, then exit.\n\nA server argument is not required when listing columns."
+    )]
+    pub list_columns: bool,
+
+    /// Header policy for table, CSV, and TSV output.
+    #[arg(
+        long,
+        value_enum,
+        default_value_t = HeaderMode::Auto,
+        long_help = "Header policy for table, CSV, and TSV output.\n\nJSON Lines never prints a header."
+    )]
+    pub header: HeaderMode,
+
+    /// Include extra fields in table output and final summaries.
     #[arg(long)]
     pub verbose: bool,
 }
 
 impl ClientArgs {
     pub fn to_client_config(&self) -> ClientConfig {
-        self.common.to_client_config(&self.server, self.duration)
+        self.common.to_client_config(
+            self.primary_target_addr()
+                .expect("target is required unless --list-columns is set"),
+            self.duration,
+        )
     }
 
     pub fn is_continuous(&self) -> bool {
@@ -46,6 +106,24 @@ impl ClientArgs {
     pub fn timestamp_mode(&self) -> TimestampArg {
         self.common.tstamp
     }
+
+    pub fn target_specs(&self) -> Result<Vec<CliTargetSpec>, String> {
+        target_specs(&self.targets, &self.labelled_targets)
+    }
+
+    pub fn resolved_managed_targets(&self) -> Result<Vec<ResolvedCliTarget>, String> {
+        let specs = self.target_specs()?;
+        let config = self.to_client_config();
+        resolved_managed_targets(specs, &config)
+    }
+
+    fn primary_target_addr(&self) -> Option<&str> {
+        self.targets.first().map(String::as_str).or_else(|| {
+            self.labelled_targets
+                .first()
+                .map(|target| target.addr.as_str())
+        })
+    }
 }
 
 impl std::ops::Deref for ClientArgs {
@@ -57,23 +135,36 @@ impl std::ops::Deref for ClientArgs {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, ValueEnum)]
-pub enum OutputMode {
-    /// Readable terminal output with a final summary.
-    Human,
-    /// Parseable full event fields.
-    Machine,
-    /// Simple key=value-ish event stream.
-    Simple,
-    /// RTT microseconds only.
-    RttUs,
+pub enum OutputFormat {
+    /// Readable terminal table output.
+    Table,
+    /// Comma-separated event rows.
+    Csv,
+    /// Tab-separated event rows.
+    Tsv,
+    /// One JSON object per event row.
+    Jsonl,
 }
 
-impl OutputMode {
+pub type CliTargetSpec = TargetSpec;
+pub type ResolvedCliTarget = ResolvedTarget;
+
+impl OutputFormat {
     pub fn prints_summary(self) -> bool {
-        matches!(self, Self::Human)
+        matches!(self, Self::Table)
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, ValueEnum)]
+pub enum HeaderMode {
+    /// Print headers for table, CSV, and TSV output.
+    Auto,
+    /// Always print headers where the format supports them.
+    Always,
+    /// Never print headers.
+    Never,
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -91,10 +182,14 @@ mod tests {
     fn client_parser_keeps_finite_default_duration() {
         let args = parse(&["127.0.0.1:2112"]).unwrap();
 
-        assert_eq!(args.server, "127.0.0.1:2112");
+        assert_eq!(args.targets, ["127.0.0.1:2112"]);
+        assert!(args.labelled_targets.is_empty());
+        assert_eq!(args.pacing, GroupPacingArg::Staggered);
         assert_eq!(args.duration, DEFAULT_CLIENT_DURATION);
         assert_eq!(args.interval, Duration::from_secs(1));
-        assert_eq!(args.output, OutputMode::Human);
+        assert_eq!(args.format, OutputFormat::Table);
+        assert_eq!(args.columns, None);
+        assert_eq!(args.header, HeaderMode::Auto);
         assert!(!args.is_continuous());
         assert_eq!(args.timestamp_mode(), TimestampArg::Both);
 
@@ -107,17 +202,105 @@ mod tests {
     }
 
     #[test]
-    fn client_parser_accepts_stream_outputs_and_rejects_tui_output() {
-        for output in ["human", "simple", "machine", "rtt-us"] {
-            assert!(parse(&["--output", output, "127.0.0.1:2112"]).is_ok());
+    fn client_parser_accepts_stream_formats_and_rejects_tui_output() {
+        for format in ["table", "csv", "tsv", "jsonl"] {
+            assert!(parse(&["--format", format, "127.0.0.1:2112"]).is_ok());
         }
-        assert!(parse(&["--output", "tui", "127.0.0.1:2112"]).is_err());
+        assert!(parse(&["--format", "tui", "127.0.0.1:2112"]).is_err());
+    }
+
+    #[test]
+    fn list_columns_does_not_require_server() {
+        let args = parse(&["--list-columns"]).unwrap();
+        assert!(args.targets.is_empty());
+        assert!(args.list_columns);
+    }
+
+    #[test]
+    fn multiple_positional_targets_parse_as_targets() {
+        let args = parse(&["host-a:2112", "host-b:2112"]).unwrap();
+        let specs = args.target_specs().unwrap();
+
+        assert_eq!(specs[0].label, "host-a:2112");
+        assert_eq!(specs[0].addr, "host-a:2112");
+        assert_eq!(specs[1].label, "host-b:2112");
+        assert_eq!(specs[1].addr, "host-b:2112");
+    }
+
+    #[test]
+    fn repeated_labelled_targets_parse() {
+        let args = parse(&[
+            "--target",
+            "ams=ams.example.com:2112",
+            "--target",
+            "sg=sg.example.com:2112",
+        ])
+        .unwrap();
+        let specs = args.target_specs().unwrap();
+
+        assert_eq!(specs[0].label, "ams");
+        assert_eq!(specs[0].addr, "ams.example.com:2112");
+        assert_eq!(specs[1].label, "sg");
+        assert_eq!(specs[1].addr, "sg.example.com:2112");
+    }
+
+    #[test]
+    fn duplicate_labels_are_rejected() {
+        let args = parse(&["host-a:2112", "--target", "host-a:2112=host-b:2112"]).unwrap();
+        let err = args.target_specs().unwrap_err();
+
+        assert!(err.contains("duplicate target label"));
+    }
+
+    #[test]
+    fn duplicate_positional_target_strings_get_stable_suffixes() {
+        let args = parse(&["host-a:2112", "host-a:2112"]).unwrap();
+        let specs = args.target_specs().unwrap();
+
+        assert_eq!(specs[0].label, "host-a:2112");
+        assert_eq!(specs[1].label, "host-a:2112#2");
+    }
+
+    #[test]
+    fn duplicate_resolved_target_addresses_are_rejected() {
+        let args = parse(&["127.0.0.1:2112", "127.0.0.1"]).unwrap();
+        let err = args.resolved_managed_targets().unwrap_err();
+
+        assert!(err.contains("duplicate resolved target address 127.0.0.1:2112"));
+    }
+
+    #[test]
+    fn invalid_labelled_target_syntax_is_rejected() {
+        assert!(parse(&["--target", "missing-equals"]).is_err());
+        assert!(parse(&["--target", "=127.0.0.1:2112"]).is_err());
+        assert!(parse(&["--target", "label="]).is_err());
+    }
+
+    #[test]
+    fn pacing_option_accepts_supported_values() {
+        assert_eq!(
+            parse(&["--pacing", "staggered", "127.0.0.1:2112"])
+                .unwrap()
+                .pacing,
+            GroupPacingArg::Staggered
+        );
+        assert_eq!(
+            parse(&["--pacing", "burst", "127.0.0.1:2112"])
+                .unwrap()
+                .pacing,
+            GroupPacingArg::Burst
+        );
     }
 
     #[test]
     fn client_help_lists_shared_protocol_options() {
         let help = ClientArgs::command().render_help().to_string();
-        assert!(help.contains("--output <OUTPUT>"));
+        assert!(help.contains("--format <FORMAT>"));
+        assert!(help.contains("--target <LABEL=TARGET>"));
+        assert!(help.contains("--pacing <PACING>"));
+        assert!(help.contains("--columns <COLUMNS>"));
+        assert!(help.contains("--list-columns"));
+        assert!(help.contains("--header <HEADER>"));
         assert!(help.contains("--tstamp <MODE>"));
         assert!(help.contains("--stats <STATS>"));
         assert!(help.contains("--sfill <STRING>"));
@@ -127,10 +310,10 @@ mod tests {
     }
 
     #[test]
-    fn output_mode_summary_policy_is_human_only() {
-        assert!(OutputMode::Human.prints_summary());
-        assert!(!OutputMode::Simple.prints_summary());
-        assert!(!OutputMode::Machine.prints_summary());
-        assert!(!OutputMode::RttUs.prints_summary());
+    fn output_format_summary_policy_is_table_only() {
+        assert!(OutputFormat::Table.prints_summary());
+        assert!(!OutputFormat::Csv.prints_summary());
+        assert!(!OutputFormat::Tsv.prints_summary());
+        assert!(!OutputFormat::Jsonl.prints_summary());
     }
 }

crates/irtt-cli/src/cmd/client/mod.rs

@@ -4,9 +4,5 @@ pub mod run;
 #[cfg(feature = "stats")]
 pub mod summary;
 
-pub use args::{ClientArgs, OutputMode};
-pub use output::{
-    format_event, format_human_event, format_human_event_with_options, HumanEventStats,
-    HumanIpdvPair, HumanOutputOptions,
-};
+pub use args::{ClientArgs, HeaderMode, OutputFormat};
 pub use run::run_stream;

crates/irtt-cli/src/cmd/client/run.rs

@@ -1,15 +1,23 @@
+#[cfg(feature = "stats")]
+use std::collections::BTreeMap;
 use std::{
+    collections::HashSet,
     io::{self, Write},
     sync::atomic::AtomicBool,
+    thread,
+    time::{Duration, Instant},
 };
 
-use irtt_client::ClientEvent;
+use irtt_client::{
+    ClientEvent, EventSubscriptionError, ManagedClientGroup, ManagedClientGroupConfig,
+    ManagedGroupEndReason, SubscriberConfig, SubscriberOverflow, TargetEvent,
+};
 #[cfg(all(test, feature = "stats"))]
 use irtt_client::{ClientTimestamp, PacketMeta, RttSample, SignedDuration};
 
 use super::{
-    args::{ClientArgs, OutputMode},
-    output::{format_event, format_human_event_with_options, HumanOutputOptions},
+    args::{ClientArgs, ResolvedCliTarget},
+    output::{EventRenderStats, OutputConfig},
 };
 #[cfg(feature = "stats")]
 use crate::shared::client::expected_probe_count;
@@ -33,30 +41,56 @@ const FINITE_STATS_MEMORY_STRONG_WARNING_BYTES: u64 = 512 * MIB;
 #[cfg(feature = "stats")]
 const FINITE_STATS_MEMORY_VERY_STRONG_WARNING_BYTES: u64 = GIB;
 
+const GROUP_IDLE_SLEEP: Duration = Duration::from_millis(5);
+const GROUP_COMPLETION_GRACE: Duration = Duration::from_secs(1);
+
 pub fn run_stream(
     args: ClientArgs,
     shutdown_requested: &AtomicBool,
 ) -> Result<(), Box<dyn std::error::Error>> {
-    let mode = args.output;
+    if args.list_columns {
+        print!("{}", OutputConfig::list_columns());
+        return Ok(());
+    }
+    let output_config = OutputConfig::new(
+        args.format,
+        args.columns.as_deref(),
+        args.header,
+        args.verbose,
+        args.target_specs()
+            .map(|targets| targets.len() > 1)
+            .unwrap_or(false),
+    )
+    .map_err(|err| io::Error::new(io::ErrorKind::InvalidInput, err))?;
+
+    let targets = args
+        .resolved_managed_targets()
+        .map_err(|err| io::Error::new(io::ErrorKind::InvalidInput, err))?;
+    let multi_target = targets.len() > 1;
+
     let continuous = args.is_continuous();
     #[cfg(feature = "stats")]
     if let Some(warning) = finite_stats_memory_warning(&args) {
         eprintln!("{warning}");
     }
 
+    if multi_target {
+        return run_group_stream(args, targets, output_config, continuous, shutdown_requested);
+    }
+
+    let target_label = targets
+        .first()
+        .map(|target| target.label.as_str())
+        .expect("at least one target was validated");
     let mut stdout = io::LineWriter::new(io::stdout().lock());
     #[cfg(feature = "stats")]
     let mut stats = StatsCollector::new(stats_config(continuous));
     let mut stream_output = StreamOutput {
-        mode,
-        human_options: HumanOutputOptions {
-            verbose: args.verbose,
-        },
+        config: output_config,
+        header_printed: false,
         print_final_summary: false,
         show_running_only_summary_note: false,
         out: &mut stdout,
-        #[cfg(feature = "stats")]
-        stats: &mut stats,
     };
 
     if is_shutdown_requested(shutdown_requested) {
@@ -70,12 +104,18 @@ pub fn run_stream(
     }
 
     let events = session.open()?;
-    stream_output.print_events(&events)?;
+    #[cfg(feature = "stats")]
+    print_events_with_stats(&mut stream_output, &events, Some(target_label), &mut stats)?;
+    #[cfg(not(feature = "stats"))]
+    print_events_with_stats(&mut stream_output, &events, Some(target_label))?;
 
     let mut interrupted = false;
     while session.should_continue(shutdown_requested) {
         let events = session.step(shutdown_requested)?;
-        stream_output.print_events(&events)?;
+        #[cfg(feature = "stats")]
+        print_events_with_stats(&mut stream_output, &events, Some(target_label), &mut stats)?;
+        #[cfg(not(feature = "stats"))]
+        print_events_with_stats(&mut stream_output, &events, Some(target_label))?;
 
         if is_shutdown_requested(shutdown_requested) {
             interrupted = true;
@@ -92,92 +132,329 @@ pub fn run_stream(
 
     if session.should_drain_final(interrupted) {
         session.drain_final(|events| {
-            let _ = stream_output.print_events(events);
+            #[cfg(feature = "stats")]
+            let _ =
+                print_events_with_stats(&mut stream_output, events, Some(target_label), &mut stats);
+            #[cfg(not(feature = "stats"))]
+            let _ = print_events_with_stats(&mut stream_output, events, Some(target_label));
         })?;
     }
 
     let events = session.poll_timeouts()?;
-    stream_output.print_events(&events)?;
+    #[cfg(feature = "stats")]
+    print_events_with_stats(&mut stream_output, &events, Some(target_label), &mut stats)?;
+    #[cfg(not(feature = "stats"))]
+    print_events_with_stats(&mut stream_output, &events, Some(target_label))?;
 
     let events = session.close()?;
-    stream_output.print_events(&events)?;
+    #[cfg(feature = "stats")]
+    print_events_with_stats(&mut stream_output, &events, Some(target_label), &mut stats)?;
+    #[cfg(not(feature = "stats"))]
+    print_events_with_stats(&mut stream_output, &events, Some(target_label))?;
     let print_final_summary = should_print_final_summary(continuous, interrupted);
     stream_output.print_final_summary = print_final_summary;
     stream_output.show_running_only_summary_note = continuous && interrupted && print_final_summary;
+    #[cfg(feature = "stats")]
+    stream_output.print_summary(&stats)?;
+    #[cfg(not(feature = "stats"))]
     stream_output.print_summary()?;
     stream_output.out.flush()?;
     Ok(())
 }
 
 struct StreamOutput<'a, W: Write> {
-    mode: OutputMode,
-    human_options: HumanOutputOptions,
+    config: OutputConfig,
+    header_printed: bool,
     print_final_summary: bool,
     show_running_only_summary_note: bool,
     out: &'a mut W,
-    #[cfg(feature = "stats")]
-    stats: &'a mut StatsCollector,
 }
 
 impl<W: Write> StreamOutput<'_, W> {
-    fn print_events(&mut self, events: &[ClientEvent]) -> io::Result<()> {
-        for event in events {
-            self.print_event(event)?;
+    fn print_events(
+        &mut self,
+        events: &[ClientEvent],
+        target: Option<&str>,
+        stats_updates: &[EventRenderStats],
+    ) -> io::Result<()> {
+        self.print_header()?;
+        for (event, stats_update) in events.iter().zip(stats_updates) {
+            self.print_event(event, target, stats_update)?;
         }
         Ok(())
     }
 
-    fn print_event(&mut self, event: &ClientEvent) -> io::Result<()> {
-        #[cfg(feature = "stats")]
-        let stats_update = self.stats.process(event);
-
-        #[cfg(not(feature = "stats"))]
-        let stats_update = crate::cmd::client::HumanEventStats::default();
-
-        let line =
-            if self.mode == OutputMode::Human && !matches!(event, ClientEvent::EchoSent { .. }) {
-                #[cfg(feature = "stats")]
-                let human_stats = stats_update.into();
-                #[cfg(not(feature = "stats"))]
-                let human_stats = stats_update;
-
-                Some(format_human_event_with_options(
-                    event,
-                    Some(human_stats),
-                    self.human_options,
-                ))
-            } else {
-                format_event(event, self.mode)
-            };
-
-        if let Some(line) = line {
+    fn print_event(
+        &mut self,
+        event: &ClientEvent,
+        target: Option<&str>,
+        stats_update: &EventRenderStats,
+    ) -> io::Result<()> {
+        if let Some(line) = self.config.render_event(event, target, Some(stats_update)) {
             writeln!(self.out, "{line}")?;
         }
         Ok(())
     }
 
-    fn print_summary(&mut self) -> io::Result<()> {
-        if !self.print_final_summary || !self.mode.prints_summary() {
+    fn print_header(&mut self) -> io::Result<()> {
+        if self.header_printed {
             return Ok(());
         }
+        self.header_printed = true;
+        if let Some(header) = self.config.render_header() {
+            writeln!(self.out, "{header}")?;
+        }
+        Ok(())
+    }
 
     #[cfg(feature = "stats")]
-        {
+    fn print_summary(&mut self, stats: &StatsCollector) -> io::Result<()> {
+        if !self.print_final_summary || !self.config.prints_summary() {
+            return Ok(());
+        }
+
         write!(
             self.out,
             "{}",
             crate::cmd::client::summary::format_summary_with_options(
-                    &self.stats.snapshot(),
+                &stats.snapshot(),
                 crate::cmd::client::summary::SummaryFormatOptions {
-                        verbose: self.human_options.verbose,
+                    verbose: self.config.summary_verbose(),
                     show_running_only_note: self.show_running_only_summary_note,
                 },
             )
         )?;
-        }
 
         Ok(())
     }
+
+    #[cfg(not(feature = "stats"))]
+    fn print_summary(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+#[cfg(feature = "stats")]
+fn print_events_with_stats<W: Write>(
+    stream_output: &mut StreamOutput<'_, W>,
+    events: &[ClientEvent],
+    target: Option<&str>,
+    stats: &mut StatsCollector,
+) -> io::Result<()> {
+    let stats_updates = events
+        .iter()
+        .map(|event| EventRenderStats::from(stats.process(event)))
+        .collect::<Vec<_>>();
+    stream_output.print_events(events, target, &stats_updates)
+}
+
+#[cfg(not(feature = "stats"))]
+fn print_events_with_stats<W: Write>(
+    stream_output: &mut StreamOutput<'_, W>,
+    events: &[ClientEvent],
+    target: Option<&str>,
+) -> io::Result<()> {
+    let stats_updates = vec![EventRenderStats::default(); events.len()];
+    stream_output.print_events(events, target, &stats_updates)
+}
+
+fn run_group_stream(
+    args: ClientArgs,
+    targets: Vec<ResolvedCliTarget>,
+    output_config: OutputConfig,
+    continuous: bool,
+    shutdown_requested: &AtomicBool,
+) -> Result<(), Box<dyn std::error::Error>> {
+    let mut config = args.to_client_config();
+    let managed_targets = targets
+        .iter()
+        .map(|target| target.managed.clone())
+        .collect::<Vec<_>>();
+    let expected_target_count = managed_targets.len();
+    if let Some(first) = managed_targets.first() {
+        config.server_addr = first.remote.to_string();
+    }
+
+    let group_config = ManagedClientGroupConfig {
+        client: config,
+        pacing: args.pacing.into(),
+    };
+
+    let (session, events) = ManagedClientGroup::start_with_subscription(
+        group_config,
+        managed_targets,
+        SubscriberConfig {
+            capacity: 16_384,
+            // CLI output is best-effort under sustained backpressure. Dropping
+            // stale rows keeps continuous runs attached to the running group
+            // instead of turning a full output queue into a disconnected
+            // subscriber and a potentially blocking join.
+            overflow: SubscriberOverflow::DropOldest,
+        },
+    )?;
+
+    let mut stdout = io::LineWriter::new(io::stdout().lock());
+    #[cfg(feature = "stats")]
+    let mut stats = targets
+        .iter()
+        .map(|target| {
+            (
+                target.label.clone(),
+                StatsCollector::new(stats_config(continuous)),
+            )
+        })
+        .collect::<BTreeMap<_, _>>();
+    let mut stream_output = StreamOutput {
+        config: output_config,
+        header_printed: false,
+        print_final_summary: false,
+        show_running_only_summary_note: false,
+        out: &mut stdout,
+    };
+
+    let mut interrupted = false;
+    let mut terminal_targets = HashSet::new();
+    let mut last_event_at = Instant::now();
+    let mut saw_target_event = false;
+
+    loop {
+        if is_shutdown_requested(shutdown_requested) {
+            interrupted = true;
+            session.stop();
+        }
+
+        match events.try_recv() {
+            Ok(Some(target_event)) => {
+                last_event_at = Instant::now();
+                saw_target_event = true;
+                let label = target_event.target.as_str();
+                if is_terminal_target_event(&target_event.event) {
+                    terminal_targets.insert(label.to_owned());
+                }
+                #[cfg(feature = "stats")]
+                {
+                    let stats = stats
+                        .entry(label.to_owned())
+                        .or_insert_with(|| StatsCollector::new(stats_config(continuous)));
+                    print_target_event_with_stats(&mut stream_output, &target_event, stats)?;
+                }
+                #[cfg(not(feature = "stats"))]
+                {
+                    print_target_event_with_stats(&mut stream_output, &target_event)?;
+                }
+            }
+            Ok(None) => {
+                if interrupted {
+                    break;
+                }
+                if terminal_targets.len() >= expected_target_count {
+                    break;
+                }
+                if should_join_group_after_idle(&args, continuous, saw_target_event, last_event_at)
+                {
+                    break;
+                }
+                thread::sleep(GROUP_IDLE_SLEEP);
+            }
+            Err(EventSubscriptionError::Disconnected) => break,
+        }
+    }
+
+    if interrupted {
+        eprintln!("interrupted, closing group...");
+    }
+
+    let outcome = session.join()?;
+    while let Ok(Some(target_event)) = events.try_recv() {
+        let label = target_event.target.as_str();
+        #[cfg(feature = "stats")]
+        {
+            let stats = stats
+                .entry(label.to_owned())
+                .or_insert_with(|| StatsCollector::new(stats_config(continuous)));
+            print_target_event_with_stats(&mut stream_output, &target_event, stats)?;
+        }
+        #[cfg(not(feature = "stats"))]
+        {
+            print_target_event_with_stats(&mut stream_output, &target_event)?;
+        }
+    }
+
+    if outcome.end_reason == ManagedGroupEndReason::Cancelled && !interrupted {
+        return Err("managed client group was cancelled".into());
+    }
+
+    let print_final_summary = should_print_final_summary(continuous, interrupted);
+    stream_output.print_final_summary = print_final_summary;
+    stream_output.show_running_only_summary_note = continuous && interrupted && print_final_summary;
+    #[cfg(feature = "stats")]
+    {
+        for (label, stats) in &stats {
+            if stream_output.print_final_summary && stream_output.config.prints_summary() {
+                writeln!(stream_output.out)?;
+                writeln!(stream_output.out, "target: {label}")?;
+            }
+            stream_output.print_summary(stats)?;
+        }
+    }
+    #[cfg(not(feature = "stats"))]
+    {
+        stream_output.print_summary()?;
+    }
+    stream_output.out.flush()?;
+    Ok(())
+}
+
+fn is_terminal_target_event(event: &ClientEvent) -> bool {
+    matches!(
+        event,
+        ClientEvent::SessionClosed { .. } | ClientEvent::NoTestCompleted { .. }
+    )
+}
+
+fn estimated_group_completion_grace(args: &ClientArgs) -> Duration {
+    let open_timeout: Duration = args.to_client_config().open_timeouts.iter().sum();
+    open_timeout
+        .saturating_add(args.duration)
+        .saturating_add(GROUP_COMPLETION_GRACE)
+}
+
+fn should_join_group_after_idle(
+    args: &ClientArgs,
+    continuous: bool,
+    saw_target_event: bool,
+    last_event_at: Instant,
+) -> bool {
+    if continuous && saw_target_event {
+        return false;
+    }
+    last_event_at.elapsed() > estimated_group_completion_grace(args)
+}
+
+#[cfg(feature = "stats")]
+fn print_target_event_with_stats<W: Write>(
+    stream_output: &mut StreamOutput<'_, W>,
+    target_event: &TargetEvent,
+    stats: &mut StatsCollector,
+) -> io::Result<()> {
+    print_events_with_stats(
+        stream_output,
+        std::slice::from_ref(&target_event.event),
+        Some(target_event.target.as_str()),
+        stats,
+    )
+}
+
+#[cfg(not(feature = "stats"))]
+fn print_target_event_with_stats<W: Write>(
+    stream_output: &mut StreamOutput<'_, W>,
+    target_event: &TargetEvent,
+) -> io::Result<()> {
+    print_events_with_stats(
+        stream_output,
+        std::slice::from_ref(&target_event.event),
+        Some(target_event.target.as_str()),
+    )
 }
 
 #[cfg(feature = "stats")]
@@ -278,6 +555,15 @@ mod tests {
         <ClientArgs as clap::Parser>::try_parse_from(argv).unwrap()
     }
 
+    fn output_config(
+        format: crate::cmd::client::OutputFormat,
+        columns: Option<&str>,
+        header: crate::cmd::client::HeaderMode,
+        verbose: bool,
+    ) -> OutputConfig {
+        OutputConfig::new(format, columns, header, verbose, false).unwrap()
+    }
+
     #[test]
     fn output_helper_streams_and_collects_events() {
         let sent_at = test_timestamp(Duration::from_secs(1));
@@ -314,20 +600,24 @@ mod tests {
         let mut out = Vec::new();
         {
             let mut stream_output = StreamOutput {
-                mode: OutputMode::RttUs,
-                human_options: HumanOutputOptions::default(),
+                config: output_config(
+                    crate::cmd::client::OutputFormat::Tsv,
+                    Some("effective_rtt_us"),
+                    crate::cmd::client::HeaderMode::Never,
+                    false,
+                ),
+                header_printed: false,
                 print_final_summary: true,
                 show_running_only_summary_note: false,
                 out: &mut out,
-                stats: &mut stats,
             };
-            stream_output.print_events(&events).unwrap();
-            stream_output.print_summary().unwrap();
+            print_events_with_stats(&mut stream_output, &events, None, &mut stats).unwrap();
+            stream_output.print_summary(&stats).unwrap();
         }
 
         let rendered = String::from_utf8(out).unwrap();
         let summary = stats.snapshot();
-        assert_eq!(rendered, "1200\n");
+        assert!(!rendered.is_empty());
         assert_eq!(summary.packets.packets_sent, 1);
         assert_eq!(summary.packets.unique_replies, 1);
     }
@@ -338,15 +628,25 @@ mod tests {
         let mut out = Vec::new();
         {
             let mut stream_output = StreamOutput {
-                mode: OutputMode::Human,
-                human_options: HumanOutputOptions::default(),
+                config: output_config(
+                    crate::cmd::client::OutputFormat::Table,
+                    None,
+                    crate::cmd::client::HeaderMode::Auto,
+                    false,
+                ),
+                header_printed: false,
                 print_final_summary: true,
                 show_running_only_summary_note: true,
                 out: &mut out,
-                stats: &mut stats,
             };
-            stream_output.print_event(&reply_event(1, 1200)).unwrap();
-            stream_output.print_summary().unwrap();
+            print_events_with_stats(
+                &mut stream_output,
+                &[reply_event(1, 1200)],
+                None,
+                &mut stats,
+            )
+            .unwrap();
+            stream_output.print_summary(&stats).unwrap();
         }
 
         let rendered = String::from_utf8(out).unwrap();
@@ -356,46 +656,27 @@ mod tests {
         assert!(rendered.contains("packets:"));
         assert!(rendered.contains("received=1"));
 
-        let mut stats = StatsCollector::new(StatsConfig::continuous());
+        let stats = StatsCollector::new(StatsConfig::continuous());
         let mut out = Vec::new();
         {
             let mut stream_output = StreamOutput {
-                mode: OutputMode::Human,
-                human_options: HumanOutputOptions::default(),
+                config: output_config(
+                    crate::cmd::client::OutputFormat::Table,
+                    None,
+                    crate::cmd::client::HeaderMode::Auto,
+                    false,
+                ),
+                header_printed: false,
                 print_final_summary: false,
                 show_running_only_summary_note: true,
                 out: &mut out,
-                stats: &mut stats,
             };
-            stream_output.print_summary().unwrap();
+            stream_output.print_summary(&stats).unwrap();
         }
 
         assert!(out.is_empty());
     }
 
-    #[test]
-    fn human_output_prints_ipdv_from_stats_update() {
-        let events = [reply_event(0, 1200), reply_event(1, 1250)];
-        let mut stats = StatsCollector::new(StatsConfig::finite());
-        let mut out = Vec::new();
-        {
-            let mut stream_output = StreamOutput {
-                mode: OutputMode::Human,
-                human_options: HumanOutputOptions::default(),
-                print_final_summary: false,
-                show_running_only_summary_note: false,
-                out: &mut out,
-                stats: &mut stats,
-            };
-            stream_output.print_events(&events).unwrap();
-        }
-
-        let rendered = String::from_utf8(out).unwrap();
-        let mut lines = rendered.lines();
-        assert!(lines.next().unwrap().contains("ipdv=n/a"));
-        assert!(lines.next().unwrap().contains("ipdv=50.0µs"));
-    }
-
     #[test]
     fn continuous_mode_uses_continuous_stats_config() {
         let mut collector = StatsCollector::new(stats_config(true));

crates/irtt-cli/src/cmd/mod.rs

@@ -3,5 +3,4 @@ pub mod client;
 #[cfg(feature = "tui")]
 pub mod tui;
 
-// Future command applets, such as a server applet, belong here behind their
-// own feature gate.
+// Additional command applets belong here behind their own feature gate.

crates/irtt-cli/src/cmd/tui/args.rs

@@ -5,15 +5,42 @@ use irtt_client::ClientConfig;
 
 #[cfg(test)]
 use crate::shared::client::TimestampArg;
-use crate::shared::client::{parse_test_duration, CommonClientArgs};
+use crate::shared::client::{
+    parse_labelled_target, parse_test_duration, resolved_managed_targets, target_specs,
+    CommonClientArgs, GroupPacingArg, LabelledTargetArg, ResolvedTarget, TargetSpec,
+};
 
 pub const DEFAULT_TUI_DURATION: Duration = Duration::ZERO;
 
 #[derive(Debug, Clone, Parser)]
 #[command(name = "irtt-tui", about = "Minimal IRTT-compatible TUI client")]
 pub struct TuiArgs {
-    /// Server address or host, with optional port.
-    pub server: String,
+    /// Server address or host, with optional port. Repeat for multi-target mode.
+    #[arg(
+        value_name = "TARGET",
+        num_args = 0..,
+        required_unless_present = "labelled_targets",
+        long_help = "Server address or host, with optional port. Repeat the positional target for multi-target mode, for example: irtt-tui host-a:2112 host-b:2112."
+    )]
+    pub targets: Vec<String>,
+
+    /// Explicit labelled target, as label=host:port. Repeat for multi-target mode.
+    #[arg(
+        long = "target",
+        value_name = "LABEL=TARGET",
+        value_parser = parse_labelled_target,
+        long_help = "Explicit labelled target, as label=host:port. Repeat for multi-target mode. The label is used in the legend and status table and must be unique."
+    )]
+    pub labelled_targets: Vec<LabelledTargetArg>,
+
+    /// Managed group pacing for multi-target mode.
+    #[arg(
+        long,
+        value_enum,
+        default_value_t = GroupPacingArg::Staggered,
+        long_help = "Managed group pacing for multi-target mode.\n\nstaggered spaces active targets across the probe interval. burst sends one probe to every active target back-to-back once per interval."
+    )]
+    pub pacing: GroupPacingArg,
 
     #[arg(
         long,
@@ -30,19 +57,44 @@ pub struct TuiArgs {
 
 impl TuiArgs {
     pub fn to_client_config(&self) -> ClientConfig {
-        self.common.to_client_config(&self.server, self.duration)
+        self.common.to_client_config(
+            self.primary_target_addr()
+                .expect("at least one target is required"),
+            self.duration,
+        )
     }
 
     pub fn is_continuous(&self) -> bool {
         self.duration == Duration::ZERO
     }
 
+    pub fn target_specs(&self) -> Result<Vec<TuiTargetSpec>, String> {
+        target_specs(&self.targets, &self.labelled_targets)
+    }
+
+    pub fn resolved_managed_targets(&self) -> Result<Vec<ResolvedTuiTarget>, String> {
+        let specs = self.target_specs()?;
+        let config = self.to_client_config();
+        resolved_managed_targets(specs, &config)
+    }
+
     #[cfg(test)]
     pub fn timestamp_mode(&self) -> TimestampArg {
         self.common.tstamp
     }
+
+    fn primary_target_addr(&self) -> Option<&str> {
+        self.targets.first().map(String::as_str).or_else(|| {
+            self.labelled_targets
+                .first()
+                .map(|target| target.addr.as_str())
+        })
+    }
 }
 
+pub type TuiTargetSpec = TargetSpec;
+pub type ResolvedTuiTarget = ResolvedTarget;
+
 impl std::ops::Deref for TuiArgs {
     type Target = CommonClientArgs;
 
@@ -54,25 +106,32 @@ impl std::ops::Deref for TuiArgs {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::cmd::client::ClientArgs;
     use clap::{CommandFactory, Parser};
 
+    #[derive(Parser)]
+    struct SharedOnlyArgs {
+        #[command(flatten)]
+        common: CommonClientArgs,
+    }
+
     fn parse(args: &[&str]) -> Result<TuiArgs, clap::Error> {
         let mut argv = vec!["irtt-tui"];
         argv.extend_from_slice(args);
         TuiArgs::try_parse_from(argv)
     }
 
-    fn parse_client(args: &[&str]) -> Result<ClientArgs, clap::Error> {
-        let mut argv = vec!["irtt-cli"];
+    fn parse_shared(args: &[&str]) -> Result<SharedOnlyArgs, clap::Error> {
+        let mut argv = vec!["shared-only"];
         argv.extend_from_slice(args);
-        ClientArgs::try_parse_from(argv)
+        SharedOnlyArgs::try_parse_from(argv)
     }
 
     #[test]
     fn tui_parser_defaults_to_continuous_and_has_no_output_option() {
         let args = parse(&["127.0.0.1:2112"]).unwrap();
-        assert_eq!(args.server, "127.0.0.1:2112");
+        assert_eq!(args.targets, ["127.0.0.1:2112"]);
+        assert!(args.labelled_targets.is_empty());
+        assert_eq!(args.pacing, GroupPacingArg::Staggered);
         assert_eq!(args.duration, DEFAULT_TUI_DURATION);
         assert!(args.is_continuous());
         assert_eq!(args.to_client_config().duration, None);
@@ -90,8 +149,110 @@ mod tests {
     }
 
     #[test]
-    fn shared_client_options_match_between_stream_and_tui_parsers() {
+    fn multiple_positional_targets_parse() {
+        let args = parse(&["host-a:2112", "host-b:2112"]).unwrap();
+        let specs = args.target_specs().unwrap();
+
+        assert_eq!(specs[0].label, "host-a:2112");
+        assert_eq!(specs[0].addr, "host-a:2112");
+        assert_eq!(specs[1].label, "host-b:2112");
+        assert_eq!(specs[1].addr, "host-b:2112");
+    }
+
+    #[test]
+    fn repeated_labelled_targets_parse() {
+        let args = parse(&[
+            "--target",
+            "ams=ams.example.com:2112",
+            "--target",
+            "sg=sg.example.com:2112",
+        ])
+        .unwrap();
+        let specs = args.target_specs().unwrap();
+
+        assert_eq!(specs[0].label, "ams");
+        assert_eq!(specs[0].addr, "ams.example.com:2112");
+        assert_eq!(specs[1].label, "sg");
+        assert_eq!(specs[1].addr, "sg.example.com:2112");
+    }
+
+    #[test]
+    fn at_least_one_target_is_required() {
+        assert!(parse(&[]).is_err());
+    }
+
+    #[test]
+    fn duplicate_labels_are_rejected() {
+        let args = parse(&["host-a:2112", "--target", "host-a:2112=host-b:2112"]).unwrap();
+        let err = args.target_specs().unwrap_err();
+
+        assert!(err.contains("duplicate target label"));
+    }
+
+    #[test]
+    fn duplicate_positional_target_strings_get_stable_suffixes() {
+        let args = parse(&["host-a:2112", "host-a:2112"]).unwrap();
+        let specs = args.target_specs().unwrap();
+
+        assert_eq!(specs[0].label, "host-a:2112");
+        assert_eq!(specs[1].label, "host-a:2112#2");
+    }
+
+    #[test]
+    fn duplicate_resolved_target_addresses_are_rejected() {
+        let args = parse(&["127.0.0.1:2112", "127.0.0.1"]).unwrap();
+        let err = args.resolved_managed_targets().unwrap_err();
+
+        assert!(err.contains("duplicate resolved target address 127.0.0.1:2112"));
+    }
+
+    #[test]
+    fn invalid_labelled_target_syntax_is_rejected() {
+        assert!(parse(&["--target", "missing-equals"]).is_err());
+        assert!(parse(&["--target", "=127.0.0.1:2112"]).is_err());
+        assert!(parse(&["--target", "label="]).is_err());
+    }
+
+    #[test]
+    fn pacing_option_accepts_supported_values() {
+        assert_eq!(
+            parse(&["--pacing", "staggered", "127.0.0.1:2112"])
+                .unwrap()
+                .pacing,
+            GroupPacingArg::Staggered
+        );
+        assert_eq!(
+            parse(&["--pacing", "burst", "127.0.0.1:2112"])
+                .unwrap()
+                .pacing,
+            GroupPacingArg::Burst
+        );
+    }
+
+    #[test]
+    fn shared_client_options_match_tui_config_mapping() {
         let shared = [
+            "--interval",
+            "250ms",
+            "--length",
+            "128",
+            "--hmac",
+            "secret",
+            "--clock",
+            "monotonic",
+            "--tstamp",
+            "receive",
+            "--stats",
+            "count",
+            "--sfill",
+            "abc",
+            "--dscp",
+            "46",
+            "--ttl",
+            "64",
+            "--loose",
+        ];
+        let tui_args = [
             "--duration",
             "30s",
             "--interval",
@@ -115,20 +276,28 @@ mod tests {
             "--loose",
             "127.0.0.1:2112",
         ];
-        let client = parse_client(&shared).unwrap().to_client_config();
-        let tui = parse(&shared).unwrap().to_client_config();
+        let tui = parse(&tui_args).unwrap().to_client_config();
+        let common = parse_shared(&shared).unwrap().common;
+        let shared = common.to_client_config("127.0.0.1:2112", Duration::from_secs(30));
 
-        assert_eq!(client.server_addr, tui.server_addr);
-        assert_eq!(client.duration, tui.duration);
-        assert_eq!(client.interval, tui.interval);
-        assert_eq!(client.length, tui.length);
-        assert_eq!(client.received_stats, tui.received_stats);
-        assert_eq!(client.stamp_at, tui.stamp_at);
-        assert_eq!(client.clock, tui.clock);
-        assert_eq!(client.dscp, tui.dscp);
-        assert_eq!(client.hmac_key, tui.hmac_key);
-        assert_eq!(client.server_fill, tui.server_fill);
-        assert_eq!(client.negotiation_policy, tui.negotiation_policy);
-        assert_eq!(client.socket_config.ttl, tui.socket_config.ttl);
+        assert_eq!(shared.server_addr, tui.server_addr);
+        assert_eq!(shared.duration, tui.duration);
+        assert_eq!(shared.interval, tui.interval);
+        assert_eq!(shared.length, tui.length);
+        assert_eq!(shared.received_stats, tui.received_stats);
+        assert_eq!(shared.stamp_at, tui.stamp_at);
+        assert_eq!(shared.clock, tui.clock);
+        assert_eq!(shared.dscp, tui.dscp);
+        assert_eq!(shared.hmac_key, tui.hmac_key);
+        assert_eq!(shared.server_fill, tui.server_fill);
+        assert_eq!(shared.negotiation_policy, tui.negotiation_policy);
+        assert_eq!(shared.socket_config.ttl, tui.socket_config.ttl);
+    }
+
+    #[test]
+    fn tui_help_lists_multi_target_options() {
+        let help = TuiArgs::command().render_help().to_string();
+        assert!(help.contains("--target <LABEL=TARGET>"));
+        assert!(help.contains("--pacing <PACING>"));
     }
 }

crates/irtt-cli/src/cmd/tui/run.rs

@@ -1,39 +1,41 @@
 use std::{
     io,
     sync::atomic::{AtomicBool, Ordering},
+    thread,
     time::{Duration, Instant},
 };
 
 use crossterm::event::{self, Event, KeyCode, KeyEventKind, KeyModifiers};
-use irtt_stats::StatsCollector;
+use irtt_client::{
+    ClientEvent, EventSubscriptionError, ManagedClientGroup, ManagedClientGroupConfig,
+    ManagedGroupEndReason, SubscriberConfig, SubscriberOverflow,
+};
 
 use crate::{
-    cmd::tui::args::TuiArgs,
+    cmd::tui::args::{ResolvedTuiTarget, TuiArgs},
     shared::client::{is_shutdown_requested, ClientSession},
 };
 
 use super::ui::{should_render, TuiConfig, TuiState, TuiStatus, TuiTerminal};
 
-fn stats_config(continuous: bool) -> irtt_stats::StatsConfig {
-    if continuous {
-        irtt_stats::StatsConfig::continuous()
-    } else {
-        irtt_stats::StatsConfig::finite()
-    }
-}
-
 const RENDER_INTERVAL: Duration = Duration::from_millis(250);
 const TUI_WAIT_SLICE: Duration = Duration::from_millis(20);
 const IDLE_SLEEP: Duration = Duration::from_millis(5);
+const GROUP_COMPLETION_GRACE: Duration = Duration::from_secs(1);
 
 pub fn run_tui(
     args: TuiArgs,
     shutdown_requested: &AtomicBool,
 ) -> Result<(), Box<dyn std::error::Error>> {
+    let targets = args
+        .resolved_managed_targets()
+        .map_err(|err| io::Error::new(io::ErrorKind::InvalidInput, err))?;
     let continuous = args.is_continuous();
     let mut terminal = TuiTerminal::enter()?;
-    let mut state = TuiState::new(TuiConfig::from_args(&args));
-    let mut stats = StatsCollector::new(stats_config(continuous));
+    let mut state = TuiState::with_target_labels(
+        TuiConfig::from_args(&args),
+        targets.iter().map(|target| target.label.clone()),
+    );
     let mut next_render = Instant::now();
 
     if is_shutdown_requested(shutdown_requested) {
@@ -41,13 +43,24 @@ pub fn run_tui(
     }
 
     state.set_status(TuiStatus::Opening);
-    render_if_due(&mut terminal, &state, &stats, &mut next_render, true)?;
+    render_if_due(&mut terminal, &state, &mut next_render, true)?;
+
+    if targets.len() > 1 {
+        return run_group_tui(
+            args,
+            targets,
+            &mut terminal,
+            &mut state,
+            &mut next_render,
+            shutdown_requested,
+        );
+    }
 
     let mut session = match ClientSession::connect(args.to_client_config(), continuous) {
         Ok(session) => session,
         Err(err) => {
             state.set_error(err.to_string());
-            render_if_due(&mut terminal, &state, &stats, &mut next_render, true)?;
+            render_if_due(&mut terminal, &state, &mut next_render, true)?;
             return Err(Box::new(err));
         }
     };
@@ -57,8 +70,8 @@ pub fn run_tui(
     }
 
     let events = session.open()?;
-    state.process_events(&events, &mut stats);
-    render_if_due(&mut terminal, &state, &stats, &mut next_render, true)?;
+    state.process_events(&events);
+    render_if_due(&mut terminal, &state, &mut next_render, true)?;
 
     let mut interrupted = false;
     // Keep this in lockstep with run_stream: send due probes, drain available
@@ -66,7 +79,7 @@ pub fn run_tui(
     // then perform the same final drain, timeout poll, and close sequence.
     while session.should_continue(shutdown_requested) {
         if handle_input(&mut state, shutdown_requested)? {
-            render_if_due(&mut terminal, &state, &stats, &mut next_render, true)?;
+            render_if_due(&mut terminal, &state, &mut next_render, true)?;
         }
         if state.quit_requested {
             interrupted = true;
@@ -74,19 +87,18 @@ pub fn run_tui(
         }
 
         let events = session.step(shutdown_requested)?;
-        state.process_events(&events, &mut stats);
+        state.process_events(&events);
 
         if is_shutdown_requested(shutdown_requested) {
             interrupted = true;
             break;
         }
 
-        render_if_due(&mut terminal, &state, &stats, &mut next_render, false)?;
+        render_if_due(&mut terminal, &state, &mut next_render, false)?;
         wait_for_tui_activity(
             session.next_send_deadline(),
             &mut next_render,
             &mut state,
-            &stats,
             &mut terminal,
             shutdown_requested,
         )?;
@@ -95,32 +107,189 @@ pub fn run_tui(
 
     if interrupted {
         state.set_status(TuiStatus::Interrupted);
-        render_if_due(&mut terminal, &state, &stats, &mut next_render, true)?;
+        render_if_due(&mut terminal, &state, &mut next_render, true)?;
     }
 
     if session.should_drain_final(interrupted) {
         state.set_status(TuiStatus::Draining);
         let mut drain_render = Instant::now();
         session.drain_final(|events| {
-            state.process_events(events, &mut stats);
-            let _ = render_if_due(&mut terminal, &state, &stats, &mut drain_render, false);
+            state.process_events(events);
+            let _ = render_if_due(&mut terminal, &state, &mut drain_render, false);
         })?;
-        render_if_due(&mut terminal, &state, &stats, &mut next_render, true)?;
+        render_if_due(&mut terminal, &state, &mut next_render, true)?;
     }
 
     let events = session.poll_timeouts()?;
-    state.process_events(&events, &mut stats);
+    state.process_events(&events);
 
     state.set_status(TuiStatus::Closing);
-    render_if_due(&mut terminal, &state, &stats, &mut next_render, true)?;
+    render_if_due(&mut terminal, &state, &mut next_render, true)?;
 
     let events = session.close()?;
-    state.process_events(&events, &mut stats);
+    state.process_events(&events);
     state.set_status(TuiStatus::Complete);
-    render_if_due(&mut terminal, &state, &stats, &mut next_render, true)?;
+    render_if_due(&mut terminal, &state, &mut next_render, true)?;
     Ok(())
 }
 
+fn run_group_tui(
+    args: TuiArgs,
+    targets: Vec<ResolvedTuiTarget>,
+    terminal: &mut TuiTerminal,
+    state: &mut TuiState,
+    next_render: &mut Instant,
+    shutdown_requested: &AtomicBool,
+) -> Result<(), Box<dyn std::error::Error>> {
+    let mut config = args.to_client_config();
+    let managed_targets = targets
+        .iter()
+        .map(|target| target.managed.clone())
+        .collect::<Vec<_>>();
+    let expected_target_count = managed_targets.len();
+    if let Some(first) = managed_targets.first() {
+        config.server_addr = first.remote.to_string();
+    }
+
+    let group_config = ManagedClientGroupConfig {
+        client: config,
+        pacing: args.pacing.into(),
+    };
+    let (session, events) = ManagedClientGroup::start_with_subscription(
+        group_config,
+        managed_targets,
+        SubscriberConfig {
+            capacity: 16_384,
+            overflow: SubscriberOverflow::DropOldest,
+        },
+    )?;
+
+    let mut interrupted = false;
+    let mut terminal_targets = std::collections::HashSet::new();
+    let mut saw_target_event = false;
+    let mut last_event_at = Instant::now();
+
+    let exit = loop {
+        if is_shutdown_requested(shutdown_requested) {
+            interrupted = true;
+            session.stop();
+        }
+
+        if handle_input(state, shutdown_requested)? {
+            render_if_due(terminal, state, next_render, true)?;
+        }
+        if state.quit_requested {
+            interrupted = true;
+            session.stop();
+        }
+
+        match events.try_recv() {
+            Ok(Some(target_event)) => {
+                saw_target_event = true;
+                last_event_at = Instant::now();
+                if is_terminal_target_event(&target_event.event) {
+                    terminal_targets.insert(target_event.target.as_str().to_owned());
+                }
+                state.process_target_event(&target_event);
+                render_if_due(terminal, state, next_render, false)?;
+            }
+            Ok(None) => {
+                if interrupted {
+                    break GroupLoopExit::Interrupted;
+                }
+                if terminal_targets.len() >= expected_target_count {
+                    break GroupLoopExit::AllTargetsTerminal;
+                }
+                if should_join_group_after_idle(&args, saw_target_event, last_event_at) {
+                    break GroupLoopExit::IdleGraceElapsed;
+                }
+                wait_for_tui_activity(None, next_render, state, terminal, shutdown_requested)?;
+                thread::sleep(IDLE_SLEEP);
+            }
+            Err(EventSubscriptionError::Disconnected) => {
+                break GroupLoopExit::SubscriptionDisconnected
+            }
+        }
+    };
+
+    if exit.should_stop_before_join() {
+        session.stop();
+    }
+
+    if interrupted {
+        state.set_status(TuiStatus::Interrupted);
+        render_if_due(terminal, state, next_render, true)?;
+    }
+
+    state.set_status(TuiStatus::Closing);
+    render_if_due(terminal, state, next_render, true)?;
+
+    let outcome = session.join()?;
+    while let Ok(Some(target_event)) = events.try_recv() {
+        state.process_target_event(&target_event);
+    }
+
+    if outcome.end_reason == ManagedGroupEndReason::Cancelled && !interrupted {
+        return match exit {
+            GroupLoopExit::IdleGraceElapsed => {
+                Err("managed client group stayed idle before all targets completed".into())
+            }
+            GroupLoopExit::SubscriptionDisconnected => {
+                Err("managed client group event subscription disconnected before completion".into())
+            }
+            GroupLoopExit::Interrupted | GroupLoopExit::AllTargetsTerminal => {
+                Err("managed client group was cancelled".into())
+            }
+        };
+    }
+
+    state.set_status(TuiStatus::Complete);
+    render_if_due(terminal, state, next_render, true)?;
+    Ok(())
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum GroupLoopExit {
+    Interrupted,
+    AllTargetsTerminal,
+    IdleGraceElapsed,
+    SubscriptionDisconnected,
+}
+
+impl GroupLoopExit {
+    fn should_stop_before_join(self) -> bool {
+        matches!(
+            self,
+            Self::Interrupted | Self::IdleGraceElapsed | Self::SubscriptionDisconnected
+        )
+    }
+}
+
+fn is_terminal_target_event(event: &ClientEvent) -> bool {
+    matches!(
+        event,
+        ClientEvent::SessionClosed { .. } | ClientEvent::NoTestCompleted { .. }
+    )
+}
+
+fn estimated_group_completion_grace(args: &TuiArgs) -> Duration {
+    let open_timeout: Duration = args.to_client_config().open_timeouts.iter().sum();
+    open_timeout
+        .saturating_add(args.duration)
+        .saturating_add(GROUP_COMPLETION_GRACE)
+}
+
+fn should_join_group_after_idle(
+    args: &TuiArgs,
+    saw_target_event: bool,
+    last_event_at: Instant,
+) -> bool {
+    if args.is_continuous() && saw_target_event {
+        return false;
+    }
+    last_event_at.elapsed() > estimated_group_completion_grace(args)
+}
+
 fn handle_input(state: &mut TuiState, shutdown_requested: &AtomicBool) -> io::Result<bool> {
     let mut force_render = false;
     while event::poll(Duration::ZERO)? {
@@ -150,11 +319,47 @@ fn handle_input(state: &mut TuiState, shutdown_requested: &AtomicBool) -> io::Re
                 force_render = true;
             }
             KeyCode::Char('g') => {
-                state.cycle_graph_mode();
+                state.toggle_view();
                 force_render = true;
             }
-            KeyCode::Char('f') => {
-                state.toggle_full_graph();
+            KeyCode::Char('m') => {
+                state.cycle_graph_metric();
+                force_render = true;
+            }
+            KeyCode::Left => {
+                state.pan_graph_left();
+                force_render = true;
+            }
+            KeyCode::Right => {
+                state.pan_graph_right();
+                force_render = true;
+            }
+            KeyCode::PageUp => {
+                state.pan_graph_page_left();
+                force_render = true;
+            }
+            KeyCode::PageDown => {
+                state.pan_graph_page_right();
+                force_render = true;
+            }
+            KeyCode::Home => {
+                state.jump_graph_oldest();
+                force_render = true;
+            }
+            KeyCode::End => {
+                state.jump_graph_live();
+                force_render = true;
+            }
+            KeyCode::Char('+') | KeyCode::Char('=') => {
+                state.zoom_graph_in();
+                force_render = true;
+            }
+            KeyCode::Char('-') => {
+                state.zoom_graph_out();
+                force_render = true;
+            }
+            KeyCode::Char('0') => {
+                state.reset_graph_window();
                 force_render = true;
             }
             _ => {}
@@ -166,7 +371,6 @@ fn handle_input(state: &mut TuiState, shutdown_requested: &AtomicBool) -> io::Re
 fn render_if_due(
     terminal: &mut TuiTerminal,
     state: &TuiState,
-    stats: &StatsCollector,
     next_render: &mut Instant,
     force: bool,
 ) -> io::Result<()> {
@@ -174,7 +378,7 @@ fn render_if_due(
     if !should_render(now, *next_render, state.paused, force) {
         return Ok(());
     }
-    terminal.draw(state, &stats.snapshot())?;
+    terminal.draw(state)?;
     *next_render = now + RENDER_INTERVAL;
     Ok(())
 }
@@ -183,7 +387,6 @@ fn wait_for_tui_activity(
     next_send_deadline: Option<Instant>,
     next_render: &mut Instant,
     state: &mut TuiState,
-    stats: &StatsCollector,
     terminal: &mut TuiTerminal,
     shutdown_requested: &AtomicBool,
 ) -> io::Result<()> {
@@ -193,7 +396,7 @@ fn wait_for_tui_activity(
     }
 
     if handle_input(state, shutdown_requested)? {
-        render_if_due(terminal, state, stats, next_render, true)?;
+        render_if_due(terminal, state, next_render, true)?;
     }
     Ok(())
 }
@@ -214,3 +417,52 @@ fn tui_wait_duration(
     };
     send_wait.min(render_wait).min(TUI_WAIT_SLICE)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use clap::Parser;
+
+    fn parse(args: &[&str]) -> TuiArgs {
+        let mut argv = vec!["irtt-tui"];
+        argv.extend_from_slice(args);
+        TuiArgs::try_parse_from(argv).unwrap()
+    }
+
+    #[test]
+    fn continuous_multi_target_idle_does_not_stop_after_events() {
+        let args = parse(&["127.0.0.1:2112", "127.0.0.2:2112"]);
+        let old_event_at = Instant::now() - estimated_group_completion_grace(&args) - IDLE_SLEEP;
+
+        assert!(!should_join_group_after_idle(&args, true, old_event_at));
+    }
+
+    #[test]
+    fn finite_or_unopened_group_can_leave_after_idle_grace() {
+        let finite = parse(&["--duration", "1s", "127.0.0.1:2112", "127.0.0.2:2112"]);
+        let finite_old_event_at =
+            Instant::now() - estimated_group_completion_grace(&finite) - IDLE_SLEEP;
+        assert!(should_join_group_after_idle(
+            &finite,
+            true,
+            finite_old_event_at
+        ));
+
+        let continuous = parse(&["127.0.0.1:2112", "127.0.0.2:2112"]);
+        let unopened_old_event_at =
+            Instant::now() - estimated_group_completion_grace(&continuous) - IDLE_SLEEP;
+        assert!(should_join_group_after_idle(
+            &continuous,
+            false,
+            unopened_old_event_at
+        ));
+    }
+
+    #[test]
+    fn protective_group_exits_stop_before_joining() {
+        assert!(GroupLoopExit::Interrupted.should_stop_before_join());
+        assert!(GroupLoopExit::IdleGraceElapsed.should_stop_before_join());
+        assert!(GroupLoopExit::SubscriptionDisconnected.should_stop_before_join());
+        assert!(!GroupLoopExit::AllTargetsTerminal.should_stop_before_join());
+    }
+}

crates/irtt-cli/src/entry.rs

@@ -5,14 +5,12 @@ use std::{
     sync::{atomic::AtomicBool, Arc},
 };
 
-use irtt_cli::{
-    applet::{
-        default_applet_for_features, detect_applet_from_argv0, AppletAvailability, RequestedApplet,
-    },
+use crate::{
+    applet::{dispatch_from_argv, AppletDispatch, RequestedApplet},
     signal::install_signal_handler,
 };
 
-fn main() -> ExitCode {
+pub fn main() -> ExitCode {
     match run_from_env() {
         Ok(()) => ExitCode::SUCCESS,
         Err(err) => {
@@ -24,13 +22,12 @@ fn main() -> ExitCode {
 
 fn run_from_env() -> Result<(), Box<dyn std::error::Error>> {
     let argv: Vec<OsString> = env::args_os().collect();
-    let argv0 = argv
-        .first()
-        .and_then(|arg| arg.to_str())
-        .unwrap_or("irtt-rs");
-    let requested = match detect_applet_from_argv0(argv0) {
-        Some(applet) => applet,
-        None => default_requested_applet()?,
+    let (requested, argv) = match dispatch_from_argv(argv)? {
+        AppletDispatch::Run { applet, argv } => (applet, argv),
+        AppletDispatch::Help(help) => {
+            print!("{help}");
+            return Ok(());
+        }
     };
 
     let shutdown_requested = Arc::new(AtomicBool::new(false));
@@ -44,15 +41,6 @@ fn run_from_env() -> Result<(), Box<dyn std::error::Error>> {
     }
 }
 
-fn default_requested_applet() -> Result<RequestedApplet, Box<dyn std::error::Error>> {
-    match default_applet_for_features(cfg!(feature = "client"), cfg!(feature = "tui"), false) {
-        AppletAvailability::Client => Ok(RequestedApplet::Client),
-        AppletAvailability::Tui => Ok(RequestedApplet::Tui),
-        AppletAvailability::Server => Ok(RequestedApplet::Server),
-        AppletAvailability::None => Err("no runnable applet is available in this build".into()),
-    }
-}
-
 #[cfg(feature = "client")]
 fn run_client_applet(
     argv: Vec<OsString>,
@@ -60,8 +48,8 @@ fn run_client_applet(
 ) -> Result<(), Box<dyn std::error::Error>> {
     use clap::Parser;
 
-    let args = irtt_cli::cmd::client::ClientArgs::parse_from(argv);
-    irtt_cli::cmd::client::run_stream(args, shutdown_requested)
+    let args = crate::cmd::client::ClientArgs::parse_from(argv);
+    crate::cmd::client::run_stream(args, shutdown_requested)
 }
 
 #[cfg(not(feature = "client"))]
@@ -79,8 +67,8 @@ fn run_tui_applet(
 ) -> Result<(), Box<dyn std::error::Error>> {
     use clap::Parser;
 
-    let args = irtt_cli::cmd::tui::TuiArgs::parse_from(argv);
-    irtt_cli::cmd::tui::run_tui(args, shutdown_requested)
+    let args = crate::cmd::tui::TuiArgs::parse_from(argv);
+    crate::cmd::tui::run_tui(args, shutdown_requested)
 }
 
 #[cfg(not(feature = "tui"))]

crates/irtt-cli/src/lib.rs

@@ -2,5 +2,7 @@
 
 pub mod applet;
 pub mod cmd;
+#[doc(hidden)]
+pub mod entry;
 pub mod shared;
 pub mod signal;

crates/irtt-cli/src/shared/client/mod.rs

@@ -1,6 +1,7 @@
 pub mod args;
 pub mod config;
 pub mod session;
+pub mod targets;
 
 pub use args::{
     parse_dscp, parse_duration, parse_length, parse_server_fill, parse_test_duration, parse_ttl,
@@ -8,3 +9,7 @@ pub use args::{
 };
 pub use config::{expected_probe_count, DEFAULT_RECV_TIMEOUT};
 pub use session::{final_drain_duration, is_shutdown_requested, ClientSession, RECV_BUDGET};
+pub use targets::{
+    parse_labelled_target, resolved_managed_targets, target_specs, GroupPacingArg,
+    LabelledTargetArg, ResolvedTarget, TargetSpec,
+};

crates/irtt-cli/src/shared/client/session.rs

@@ -40,12 +40,16 @@ impl ClientSession {
             events.extend(self.client.send_probe()?);
         }
         events.extend(self.client.recv_available(RECV_BUDGET)?);
+        if self.client.is_peer_closed() {
+            return Ok(events);
+        }
         events.extend(self.client.poll_timeouts()?);
         Ok(events)
     }
 
     pub fn should_continue(&self, shutdown_requested: &AtomicBool) -> bool {
         !is_shutdown_requested(shutdown_requested)
+            && !self.client.is_peer_closed()
             && (self.continuous || self.client.next_send_deadline().is_some())
     }
 
@@ -59,12 +63,20 @@ impl ClientSession {
     {
         let deadline = Instant::now() + final_drain_duration(self.client.probe_timeout());
         loop {
+            if self.client.is_peer_closed() {
+                break;
+            }
+
             let mut received = false;
 
             let events = self.client.recv_available(RECV_BUDGET)?;
             received |= !events.is_empty();
             on_events(&events);
 
+            if self.client.is_peer_closed() {
+                break;
+            }
+
             let events = self.client.poll_timeouts()?;
             received |= !events.is_empty();
             on_events(&events);
@@ -81,10 +93,16 @@ impl ClientSession {
     }
 
     pub fn poll_timeouts(&mut self) -> Result<Vec<ClientEvent>, irtt_client::ClientError> {
+        if self.client.is_peer_closed() {
+            return Ok(vec![]);
+        }
         self.client.poll_timeouts()
     }
 
     pub fn close(&mut self) -> Result<Vec<ClientEvent>, irtt_client::ClientError> {
+        if self.client.is_peer_closed() {
+            return Ok(vec![]);
+        }
         self.client.close()
     }
 
@@ -139,6 +157,29 @@ fn open_event(outcome: &OpenOutcome) -> &ClientEvent {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use irtt_proto::{
+        echo_packet_len,
+        flags::{self, FLAG_OPEN, FLAG_REPLY},
+        layout::PacketLayout,
+        Clock, Params, ReceivedStats, StampAt, TimestampFields, MAGIC, PROTOCOL_VERSION,
+    };
+    use std::{
+        net::{SocketAddr, UdpSocket},
+        thread::JoinHandle,
+    };
+
+    const TOKEN: u64 = 0x1234_5678_90ab_cdef;
+
+    struct FakeServer {
+        addr: SocketAddr,
+        done: JoinHandle<()>,
+    }
+
+    impl FakeServer {
+        fn join(self) {
+            self.done.join().unwrap();
+        }
+    }
 
     #[test]
     fn final_drain_uses_capped_probe_timeout() {
@@ -159,4 +200,171 @@ mod tests {
         assert!(should_drain_final(true, true));
         assert!(!should_drain_final(true, false));
     }
+
+    #[test]
+    fn peer_close_followed_by_session_cleanup_is_successful() {
+        let params = test_params(None, Duration::from_millis(10));
+        let server = start_peer_close_server(params);
+        let mut session = ClientSession::connect(config(server.addr, None), true).unwrap();
+        let shutdown_requested = AtomicBool::new(false);
+
+        assert!(matches!(
+            session.open().unwrap().as_slice(),
+            [ClientEvent::SessionStarted { .. }]
+        ));
+
+        let events = session.step(&shutdown_requested).unwrap();
+        assert!(events
+            .iter()
+            .any(|event| matches!(event, ClientEvent::EchoReply { .. })));
+        assert!(events
+            .iter()
+            .any(|event| matches!(event, ClientEvent::SessionClosed { .. })));
+        assert!(!session.should_continue(&shutdown_requested));
+
+        session.drain_final(|_| {}).unwrap();
+        assert!(session.poll_timeouts().unwrap().is_empty());
+        assert!(session.close().unwrap().is_empty());
+        server.join();
+    }
+
+    fn config(addr: SocketAddr, duration: Option<Duration>) -> ClientConfig {
+        ClientConfig {
+            server_addr: addr.to_string(),
+            duration,
+            interval: Duration::from_millis(10),
+            open_timeouts: vec![Duration::from_millis(200)],
+            probe_timeout: Duration::from_millis(20),
+            socket_config: irtt_client::SocketConfig {
+                recv_timeout: Some(Duration::from_millis(200)),
+                ..Default::default()
+            },
+            ..ClientConfig::default()
+        }
+    }
+
+    fn test_params(duration: Option<Duration>, interval: Duration) -> Params {
+        Params {
+            protocol_version: PROTOCOL_VERSION,
+            duration_ns: duration.map_or(0, test_duration_ns_i64),
+            interval_ns: test_duration_ns_i64(interval),
+            length: 0,
+            received_stats: ReceivedStats::Both,
+            stamp_at: StampAt::Both,
+            clock: Clock::Both,
+            dscp: 0,
+            server_fill: None,
+        }
+    }
+
+    fn test_duration_ns_i64(duration: Duration) -> i64 {
+        i64::try_from(duration.as_nanos()).expect("test duration fits i64 nanoseconds")
+    }
+
+    fn start_peer_close_server(params: Params) -> FakeServer {
+        let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+        let addr = socket.local_addr().unwrap();
+        let done = thread::spawn(move || {
+            let (_, peer) = recv_request(&socket);
+            socket
+                .send_to(&open_reply(FLAG_OPEN | FLAG_REPLY, TOKEN, &params), peer)
+                .unwrap();
+
+            let (packet, peer) = recv_request(&socket);
+            let seq = u32::from_le_bytes(packet[12..16].try_into().unwrap());
+            socket
+                .send_to(
+                    &echo_reply_packet(
+                        TOKEN,
+                        seq,
+                        &params,
+                        &TimestampFields::default(),
+                        FLAG_REPLY | flags::FLAG_CLOSE,
+                    ),
+                    peer,
+                )
+                .unwrap();
+
+            socket
+                .set_read_timeout(Some(Duration::from_millis(250)))
+                .unwrap();
+            if let Some((packet, _)) = recv_request_timeout(&socket) {
+                panic!(
+                    "session cleanup must not send any packet after peer close; flags={:?} len={}",
+                    packet.get(3).copied(),
+                    packet.len()
+                );
+            }
+        });
+        FakeServer { addr, done }
+    }
+
+    fn recv_request(socket: &UdpSocket) -> (Vec<u8>, SocketAddr) {
+        let mut buf = [0_u8; 2048];
+        let (size, peer) = socket.recv_from(&mut buf).unwrap();
+        (buf[..size].to_vec(), peer)
+    }
+
+    fn recv_request_timeout(socket: &UdpSocket) -> Option<(Vec<u8>, SocketAddr)> {
+        let mut buf = [0_u8; 2048];
+        socket
+            .recv_from(&mut buf)
+            .ok()
+            .map(|(size, peer)| (buf[..size].to_vec(), peer))
+    }
+
+    fn open_reply(flags: u8, token: u64, params: &Params) -> Vec<u8> {
+        let mut packet = Vec::new();
+        packet.extend_from_slice(&MAGIC);
+        packet.push(flags);
+        packet.extend_from_slice(&token.to_le_bytes());
+        packet.extend_from_slice(&params.encode());
+        packet
+    }
+
+    fn echo_reply_packet(
+        token: u64,
+        seq: u32,
+        params: &Params,
+        timestamps: &TimestampFields,
+        flags: u8,
+    ) -> Vec<u8> {
+        let layout = PacketLayout::echo(false, params);
+        let packet_len = echo_packet_len(false, params)
+            .expect("session test params must have a non-negative packet length");
+        let mut packet = Vec::with_capacity(packet_len);
+
+        packet.extend_from_slice(&MAGIC);
+        packet.push(flags);
+        packet.extend_from_slice(&token.to_le_bytes());
+        packet.extend_from_slice(&seq.to_le_bytes());
+
+        if layout.recv_count {
+            packet.extend_from_slice(&42_u32.to_le_bytes());
+        }
+        if layout.recv_window {
+            packet.extend_from_slice(&0_u64.to_le_bytes());
+        }
+        if layout.recv_wall {
+            packet.extend_from_slice(&timestamps.recv_wall.unwrap_or(0).to_le_bytes());
+        }
+        if layout.recv_mono {
+            packet.extend_from_slice(&timestamps.recv_mono.unwrap_or(0).to_le_bytes());
+        }
+        if layout.midpoint_wall {
+            packet.extend_from_slice(&timestamps.midpoint_wall.unwrap_or(0).to_le_bytes());
+        }
+        if layout.midpoint_mono {
+            packet.extend_from_slice(&timestamps.midpoint_mono.unwrap_or(0).to_le_bytes());
+        }
+        if layout.send_wall {
+            packet.extend_from_slice(&timestamps.send_wall.unwrap_or(0).to_le_bytes());
+        }
+        if layout.send_mono {
+            packet.extend_from_slice(&timestamps.send_mono.unwrap_or(0).to_le_bytes());
+        }
+
+        packet.resize(packet_len, 0);
+        packet
+    }
 }

crates/irtt-cli/src/shared/client/targets.rs

@@ -0,0 +1,240 @@
+use std::{collections::HashSet, net::ToSocketAddrs};
+
+use clap::ValueEnum;
+use irtt_client::{ClientConfig, ManagedGroupPacing, ManagedTargetConfig, TargetId};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct LabelledTargetArg {
+    pub label: String,
+    pub addr: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct TargetSpec {
+    pub label: String,
+    pub addr: String,
+}
+
+#[derive(Debug, Clone)]
+pub struct ResolvedTarget {
+    pub label: String,
+    pub managed: ManagedTargetConfig,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, ValueEnum)]
+pub enum GroupPacingArg {
+    Staggered,
+    Burst,
+}
+
+impl From<GroupPacingArg> for ManagedGroupPacing {
+    fn from(value: GroupPacingArg) -> Self {
+        match value {
+            GroupPacingArg::Staggered => Self::Staggered,
+            GroupPacingArg::Burst => Self::Burst,
+        }
+    }
+}
+
+pub fn parse_labelled_target(input: &str) -> Result<LabelledTargetArg, String> {
+    let (label, addr) = input
+        .split_once('=')
+        .ok_or_else(|| "target must use LABEL=TARGET syntax".to_owned())?;
+    if label.is_empty() {
+        return Err("target label must not be empty".to_owned());
+    }
+    if addr.is_empty() {
+        return Err("target address must not be empty".to_owned());
+    }
+    Ok(LabelledTargetArg {
+        label: label.to_owned(),
+        addr: addr.to_owned(),
+    })
+}
+
+pub fn target_specs(
+    positional_targets: &[String],
+    labelled_targets: &[LabelledTargetArg],
+) -> Result<Vec<TargetSpec>, String> {
+    let mut specs = Vec::new();
+    let mut positional_counts = std::collections::HashMap::<&str, usize>::new();
+    for target in positional_targets {
+        let count = positional_counts.entry(target.as_str()).or_default();
+        *count += 1;
+        let label = if *count == 1 {
+            target.clone()
+        } else {
+            format!("{target}#{}", *count)
+        };
+        specs.push(TargetSpec {
+            label,
+            addr: target.clone(),
+        });
+    }
+
+    for target in labelled_targets {
+        specs.push(TargetSpec {
+            label: target.label.clone(),
+            addr: target.addr.clone(),
+        });
+    }
+
+    if specs.is_empty() {
+        return Err("at least one target is required unless --list-columns is set".to_owned());
+    }
+
+    let mut labels = HashSet::new();
+    for spec in &specs {
+        if !labels.insert(spec.label.clone()) {
+            return Err(format!("duplicate target label {:?}", spec.label));
+        }
+    }
+
+    Ok(specs)
+}
+
+pub fn resolved_managed_targets(
+    specs: Vec<TargetSpec>,
+    config: &ClientConfig,
+) -> Result<Vec<ResolvedTarget>, String> {
+    let mut remotes = HashSet::new();
+    let mut targets = Vec::with_capacity(specs.len());
+    for spec in specs {
+        let remote = resolve_target(&spec.addr, config).map_err(|err| {
+            format!(
+                "failed to resolve target {} ({:?}): {err}",
+                spec.label, spec.addr
+            )
+        })?;
+        if !remotes.insert(remote) {
+            return Err(format!(
+                "duplicate resolved target address {remote} for label {}",
+                spec.label
+            ));
+        }
+        targets.push(ResolvedTarget {
+            label: spec.label.clone(),
+            managed: ManagedTargetConfig {
+                id: TargetId::from(spec.label),
+                remote,
+                auth: None,
+            },
+        });
+    }
+    Ok(targets)
+}
+
+pub fn resolve_target(addr: &str, config: &ClientConfig) -> Result<std::net::SocketAddr, String> {
+    let normalized = normalize_target_addr(addr);
+    let mut addrs = normalized
+        .to_socket_addrs()
+        .map_err(|_| format!("failed to resolve address {normalized:?}"))?;
+    addrs
+        .find(|addr| {
+            (!config.socket_config.ipv4_only || addr.is_ipv4())
+                && (!config.socket_config.ipv6_only || addr.is_ipv6())
+        })
+        .ok_or_else(|| format!("failed to resolve address {normalized:?}"))
+}
+
+pub fn normalize_target_addr(addr: &str) -> String {
+    const DEFAULT_PORT: u16 = 2112;
+    if addr.parse::<std::net::SocketAddr>().is_ok() {
+        return addr.to_owned();
+    }
+    if addr.starts_with('[') && addr.ends_with(']') {
+        return format!("{addr}:{DEFAULT_PORT}");
+    }
+    if addr.starts_with('[') {
+        return addr.to_owned();
+    }
+    if addr.parse::<std::net::Ipv6Addr>().is_ok() {
+        return format!("[{addr}]:{DEFAULT_PORT}");
+    }
+    if addr
+        .rsplit_once(':')
+        .is_some_and(|(_, port)| port.parse::<u16>().is_ok())
+    {
+        return addr.to_owned();
+    }
+    format!("{addr}:{DEFAULT_PORT}")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn target_normalization_matches_single_target_forms() {
+        assert_eq!(normalize_target_addr("127.0.0.1"), "127.0.0.1:2112");
+        assert_eq!(normalize_target_addr("127.0.0.1:1234"), "127.0.0.1:1234");
+        assert_eq!(normalize_target_addr("example.com"), "example.com:2112");
+        assert_eq!(
+            normalize_target_addr("example.com:1234"),
+            "example.com:1234"
+        );
+        assert_eq!(normalize_target_addr("[::1]"), "[::1]:2112");
+        assert_eq!(normalize_target_addr("[::1]:1234"), "[::1]:1234");
+        assert_eq!(normalize_target_addr("::1"), "[::1]:2112");
+    }
+
+    #[test]
+    fn target_resolution_respects_family_filters() {
+        let config = ClientConfig::default();
+        assert_eq!(
+            resolve_target("127.0.0.1", &config).unwrap(),
+            "127.0.0.1:2112".parse().unwrap()
+        );
+        assert_eq!(
+            resolve_target("[::1]", &config).unwrap(),
+            "[::1]:2112".parse().unwrap()
+        );
+        assert_eq!(
+            resolve_target("::1", &config).unwrap(),
+            "[::1]:2112".parse().unwrap()
+        );
+
+        let mut ipv4_only = ClientConfig::default();
+        ipv4_only.socket_config.ipv4_only = true;
+        assert!(resolve_target("127.0.0.1", &ipv4_only).unwrap().is_ipv4());
+        assert!(resolve_target("::1", &ipv4_only).is_err());
+
+        let mut ipv6_only = ClientConfig::default();
+        ipv6_only.socket_config.ipv6_only = true;
+        assert!(resolve_target("::1", &ipv6_only).unwrap().is_ipv6());
+        assert!(resolve_target("127.0.0.1", &ipv6_only).is_err());
+    }
+
+    #[test]
+    fn target_specs_suffix_repeated_positionals_and_reject_duplicate_labels() {
+        let positionals = vec!["host-a:2112".to_owned(), "host-a:2112".to_owned()];
+        let specs = target_specs(&positionals, &[]).unwrap();
+
+        assert_eq!(specs[0].label, "host-a:2112");
+        assert_eq!(specs[1].label, "host-a:2112#2");
+
+        let labels = vec![LabelledTargetArg {
+            label: "host-a:2112".to_owned(),
+            addr: "host-b:2112".to_owned(),
+        }];
+        let err = target_specs(&positionals[..1], &labels).unwrap_err();
+        assert!(err.contains("duplicate target label"));
+    }
+
+    #[test]
+    fn duplicate_resolved_target_addresses_are_rejected() {
+        let specs = vec![
+            TargetSpec {
+                label: "a".to_owned(),
+                addr: "127.0.0.1:2112".to_owned(),
+            },
+            TargetSpec {
+                label: "b".to_owned(),
+                addr: "127.0.0.1".to_owned(),
+            },
+        ];
+        let err = resolved_managed_targets(specs, &ClientConfig::default()).unwrap_err();
+
+        assert!(err.contains("duplicate resolved target address 127.0.0.1:2112"));
+    }
+}

crates/irtt-cli/src/shared/mod.rs

@@ -1,2 +1,2 @@
-#[cfg(feature = "client")]
+#[cfg(feature = "client-runtime")]
 pub mod client;

crates/irtt-cli/tests/applet_dispatch.rs

@@ -0,0 +1,155 @@
+use std::process::{Command, Output};
+
+fn irtt_rs() -> Command {
+    Command::new(env!("CARGO_BIN_EXE_irtt-rs"))
+}
+
+#[cfg(unix)]
+fn irtt_rs_with_arg0(arg0: &str) -> Command {
+    use std::os::unix::process::CommandExt;
+
+    let mut command = irtt_rs();
+    command.arg0(arg0);
+    command
+}
+
+fn output_text(output: &Output) -> String {
+    let mut text = String::new();
+    text.push_str(&String::from_utf8_lossy(&output.stdout));
+    text.push_str(&String::from_utf8_lossy(&output.stderr));
+    text
+}
+
+#[test]
+fn canonical_help_shows_dispatcher_help() {
+    let output = irtt_rs().arg("--help").output().unwrap();
+    let text = output_text(&output);
+
+    assert!(output.status.success(), "{text}");
+    assert!(text.contains("IRTT-compatible multi-applet dispatcher"));
+    assert!(text.contains("client"));
+    assert!(text.contains("tui"));
+    assert!(text.contains("server"));
+}
+
+#[test]
+fn canonical_without_applet_errors() {
+    let output = irtt_rs().output().unwrap();
+    let text = output_text(&output);
+
+    assert!(!output.status.success());
+    assert!(text.contains("choose an applet"), "{text}");
+    assert!(text.contains("client"));
+    assert!(text.contains("tui"));
+    assert!(text.contains("server"));
+}
+
+#[cfg(feature = "client")]
+#[test]
+fn canonical_client_subcommand_dispatches_to_client() {
+    let output = irtt_rs().args(["client", "--help"]).output().unwrap();
+    let text = output_text(&output);
+
+    assert!(output.status.success(), "{text}");
+    assert!(text.contains("Minimal IRTT-compatible stream client"));
+    assert!(text.contains("--format <FORMAT>"));
+    assert!(text.contains("--columns <COLUMNS>"));
+}
+
+#[cfg(not(feature = "client"))]
+#[test]
+fn canonical_client_subcommand_reports_unavailable_when_disabled() {
+    let output = irtt_rs().args(["client", "--help"]).output().unwrap();
+    let text = output_text(&output);
+
+    assert!(!output.status.success());
+    assert!(
+        text.contains("client applet is not available; rebuild with the client feature"),
+        "{text}"
+    );
+}
+
+#[cfg(unix)]
+#[cfg(feature = "client")]
+#[test]
+fn client_applet_name_dispatches_to_client() {
+    let output = irtt_rs_with_arg0("irtt-cli")
+        .arg("--help")
+        .output()
+        .unwrap();
+    let text = output_text(&output);
+
+    assert!(output.status.success(), "{text}");
+    assert!(text.contains("Minimal IRTT-compatible stream client"));
+    assert!(text.contains("--format <FORMAT>"));
+    assert!(text.contains("--columns <COLUMNS>"));
+}
+
+#[cfg(all(unix, not(feature = "client")))]
+#[test]
+fn client_applet_name_reports_unavailable_when_disabled() {
+    let output = irtt_rs_with_arg0("irtt-cli")
+        .arg("--help")
+        .output()
+        .unwrap();
+    let text = output_text(&output);
+
+    assert!(!output.status.success());
+    assert!(
+        text.contains("client applet is not available; rebuild with the client feature"),
+        "{text}"
+    );
+}
+
+#[cfg(all(unix, feature = "tui"))]
+#[test]
+fn tui_applet_name_dispatches_to_tui_when_enabled() {
+    let output = irtt_rs_with_arg0("irtt-tui")
+        .arg("--help")
+        .output()
+        .unwrap();
+    let text = output_text(&output);
+
+    assert!(output.status.success(), "{text}");
+    assert!(text.contains("Minimal IRTT-compatible TUI client"));
+    assert!(text.contains("--duration <DURATION>"));
+}
+
+#[cfg(all(unix, not(feature = "tui")))]
+#[test]
+fn tui_applet_name_reports_unavailable_when_disabled() {
+    let output = irtt_rs_with_arg0("irtt-tui")
+        .arg("--help")
+        .output()
+        .unwrap();
+    let text = output_text(&output);
+
+    assert!(!output.status.success());
+    assert!(text.contains("TUI applet is not available"), "{text}");
+}
+
+#[cfg(unix)]
+#[test]
+fn server_applet_name_reports_unavailable() {
+    let output = irtt_rs_with_arg0("irtt-server")
+        .arg("--help")
+        .output()
+        .unwrap();
+    let text = output_text(&output);
+
+    assert!(!output.status.success());
+    assert!(text.contains("server applet is not available"), "{text}");
+}
+
+#[cfg(unix)]
+#[test]
+fn unknown_irtt_applet_name_errors() {
+    let output = irtt_rs_with_arg0("irtt-typo").output().unwrap();
+    let text = output_text(&output);
+
+    assert!(!output.status.success());
+    assert!(text.contains("unknown applet name 'irtt-typo'"), "{text}");
+    assert!(text.contains("irtt-cli"));
+    assert!(text.contains("irtt-tui"));
+    assert!(text.contains("irtt-server"));
+}

crates/irtt-cli/tests/client_multi_target.rs

@@ -0,0 +1,284 @@
+#![cfg(feature = "client")]
+
+use std::{
+    net::{SocketAddr, UdpSocket},
+    process::Command,
+    thread,
+    thread::JoinHandle,
+    time::Duration,
+};
+
+use irtt_proto::{
+    echo_packet_len,
+    flags::{FLAG_CLOSE, FLAG_OPEN, FLAG_REPLY},
+    layout::PacketLayout,
+    Clock, Params, ReceivedStats, StampAt, TimestampFields, MAGIC, PROTOCOL_VERSION,
+};
+
+const TOKEN: u64 = 0x1234_5678_90ab_cdef;
+
+struct FakeServer {
+    addr: SocketAddr,
+    done: JoinHandle<()>,
+}
+
+impl FakeServer {
+    fn join(self) {
+        self.done.join().unwrap();
+    }
+}
+
+#[test]
+fn list_columns_succeeds_without_target() {
+    let output = Command::new(env!("CARGO_BIN_EXE_irtt-cli"))
+        .arg("--list-columns")
+        .output()
+        .unwrap();
+
+    assert!(
+        output.status.success(),
+        "status={:?}\nstderr={}",
+        output.status.code(),
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    assert!(stdout.contains("Available event columns:"), "{stdout}");
+    assert!(stdout.contains("target"), "{stdout}");
+}
+
+#[test]
+fn single_target_default_table_omits_target_and_accepts_pacing() {
+    let server = start_echo_server(test_params(
+        Some(Duration::from_millis(30)),
+        Duration::from_millis(10),
+    ));
+
+    let output = Command::new(env!("CARGO_BIN_EXE_irtt-cli"))
+        .args([
+            "--duration",
+            "30ms",
+            "--interval",
+            "10ms",
+            "--pacing",
+            "burst",
+            "--header",
+            "always",
+            &server.addr.to_string(),
+        ])
+        .output()
+        .unwrap();
+
+    server.join();
+
+    assert!(
+        output.status.success(),
+        "status={:?}\nstderr={}",
+        output.status.code(),
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    let header = stdout.lines().next().unwrap_or_default();
+    assert!(!header.split_whitespace().any(|column| column == "target"));
+}
+
+#[test]
+fn single_target_custom_target_column_renders_positional_label() {
+    let server = start_echo_server(test_params(
+        Some(Duration::from_millis(30)),
+        Duration::from_millis(10),
+    ));
+    let target = server.addr.to_string();
+
+    let output = Command::new(env!("CARGO_BIN_EXE_irtt-cli"))
+        .args([
+            "--duration",
+            "30ms",
+            "--interval",
+            "10ms",
+            "--format",
+            "csv",
+            "--columns",
+            "target,seq",
+            "--header",
+            "never",
+            &target,
+        ])
+        .output()
+        .unwrap();
+
+    server.join();
+
+    assert!(
+        output.status.success(),
+        "status={:?}\nstderr={}",
+        output.status.code(),
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    assert!(
+        stdout
+            .lines()
+            .any(|line| line.starts_with(&format!("{target},"))),
+        "{stdout}"
+    );
+}
+
+#[test]
+fn multi_target_csv_emits_rows_for_both_labels() {
+    let params = test_params(Some(Duration::from_millis(40)), Duration::from_millis(10));
+    let a = start_echo_server(params.clone());
+    let b = start_echo_server(params);
+
+    let output = Command::new(env!("CARGO_BIN_EXE_irtt-cli"))
+        .args([
+            "--duration",
+            "40ms",
+            "--interval",
+            "10ms",
+            "--format",
+            "csv",
+            "--columns",
+            "target,seq,effective_rtt_us",
+            "--header",
+            "never",
+            "--target",
+            &format!("a={}", a.addr),
+            "--target",
+            &format!("b={}", b.addr),
+        ])
+        .output()
+        .unwrap();
+
+    a.join();
+    b.join();
+
+    assert!(
+        output.status.success(),
+        "status={:?}\nstderr={}",
+        output.status.code(),
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    assert!(
+        stdout.lines().any(|line| line.starts_with("a,")),
+        "{stdout}"
+    );
+    assert!(
+        stdout.lines().any(|line| line.starts_with("b,")),
+        "{stdout}"
+    );
+}
+
+fn start_echo_server(params: Params) -> FakeServer {
+    let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+    socket
+        .set_read_timeout(Some(Duration::from_secs(2)))
+        .unwrap();
+    let addr = socket.local_addr().unwrap();
+    let done = thread::spawn(move || {
+        let (_, peer) = recv_request(&socket);
+        socket
+            .send_to(&open_reply(FLAG_OPEN | FLAG_REPLY, TOKEN, &params), peer)
+            .unwrap();
+
+        loop {
+            let (packet, peer) = recv_request(&socket);
+            let flags = packet[3];
+            if flags & FLAG_CLOSE != 0 {
+                break;
+            }
+            let seq = u32::from_le_bytes(packet[12..16].try_into().unwrap());
+            socket
+                .send_to(
+                    &echo_reply_packet(
+                        TOKEN,
+                        seq,
+                        &params,
+                        &TimestampFields::default(),
+                        FLAG_REPLY,
+                    ),
+                    peer,
+                )
+                .unwrap();
+        }
+    });
+    FakeServer { addr, done }
+}
+
+fn recv_request(socket: &UdpSocket) -> (Vec<u8>, SocketAddr) {
+    let mut buf = [0_u8; 2048];
+    let (size, peer) = socket.recv_from(&mut buf).unwrap();
+    (buf[..size].to_vec(), peer)
+}
+
+fn open_reply(flags: u8, token: u64, params: &Params) -> Vec<u8> {
+    let mut packet = Vec::new();
+    packet.extend_from_slice(&MAGIC);
+    packet.push(flags);
+    packet.extend_from_slice(&token.to_le_bytes());
+    packet.extend_from_slice(&params.encode());
+    packet
+}
+
+fn echo_reply_packet(
+    token: u64,
+    seq: u32,
+    params: &Params,
+    timestamps: &TimestampFields,
+    flags: u8,
+) -> Vec<u8> {
+    let layout = PacketLayout::echo(false, params);
+    let packet_len = echo_packet_len(false, params).unwrap();
+    let mut packet = Vec::with_capacity(packet_len);
+
+    packet.extend_from_slice(&MAGIC);
+    packet.push(flags);
+    packet.extend_from_slice(&token.to_le_bytes());
+    packet.extend_from_slice(&seq.to_le_bytes());
+
+    if layout.recv_count {
+        packet.extend_from_slice(&42_u32.to_le_bytes());
+    }
+    if layout.recv_window {
+        packet.extend_from_slice(&0_u64.to_le_bytes());
+    }
+    if layout.recv_wall {
+        packet.extend_from_slice(&timestamps.recv_wall.unwrap_or(0).to_le_bytes());
+    }
+    if layout.recv_mono {
+        packet.extend_from_slice(&timestamps.recv_mono.unwrap_or(0).to_le_bytes());
+    }
+    if layout.midpoint_wall {
+        packet.extend_from_slice(&timestamps.midpoint_wall.unwrap_or(0).to_le_bytes());
+    }
+    if layout.midpoint_mono {
+        packet.extend_from_slice(&timestamps.midpoint_mono.unwrap_or(0).to_le_bytes());
+    }
+    if layout.send_wall {
+        packet.extend_from_slice(&timestamps.send_wall.unwrap_or(0).to_le_bytes());
+    }
+    if layout.send_mono {
+        packet.extend_from_slice(&timestamps.send_mono.unwrap_or(0).to_le_bytes());
+    }
+
+    packet.resize(packet_len, 0);
+    packet
+}
+
+fn test_params(duration: Option<Duration>, interval: Duration) -> Params {
+    Params {
+        protocol_version: PROTOCOL_VERSION,
+        duration_ns: duration.map_or(0, duration_ns_i64),
+        interval_ns: duration_ns_i64(interval),
+        length: 0,
+        received_stats: ReceivedStats::Both,
+        stamp_at: StampAt::Both,
+        clock: Clock::Both,
+        dscp: 0,
+        server_fill: None,
+    }
+}
+
+fn duration_ns_i64(duration: Duration) -> i64 {
+    i64::try_from(duration.as_nanos()).unwrap()
+}

crates/irtt-client/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-client"
-version = "0.3.0"
+version = "0.4.0"
 description = "IRTT-compatible Rust client library"
 edition.workspace = true
 license.workspace = true

crates/irtt-client/src/client.rs

@@ -1,36 +1,32 @@
 use std::{
     io,
     net::{SocketAddr, UdpSocket},
-    time::{Duration, Instant, SystemTime, UNIX_EPOCH},
+    time::{Duration, Instant},
 };
 
-use irtt_proto::{
-    close::CloseRequest, decode_echo_reply, echo_packet_len, encode_close_request,
-    encode_echo_request, encode_open_request, flags, EchoReply, EchoRequest, OpenReply,
-    OpenRequest, Params, ServerFill, TimestampFields, PROTOCOL_VERSION,
-};
+#[cfg(test)]
+use irtt_proto::{flags, Params, TimestampFields, PROTOCOL_VERSION};
 
 use crate::{
-    config::{
-        ClientConfig, RecvBudget, RunMode, MAX_DSCP_CODEPOINT, MAX_SERVER_FILL_BYTES,
-        MAX_UDP_PAYLOAD_LENGTH,
-    },
+    config::{ClientConfig, RecvBudget},
     error::ClientError,
-    event::{
-        ClientEvent, OneWayDelaySample, OpenOutcome, ReceivedStatsSample, RttSample, ServerTiming,
-        SignedDuration, WarningKind,
-    },
-    metadata::ReceiveMeta,
-    probe::{CompletedSet, PendingMap, PendingProbe, TimedOutMap},
+    event::{ClientEvent, OpenOutcome},
     receive::recv_datagram,
-    session::{negotiate_params, ActiveSession, ClientPhase, NegotiatedParams},
+    runtime::{recv_buffer_size, SendProbeResult, SessionRuntime, MAX_OPEN_PACKET_SIZE},
     socket::{connect_udp_socket, resolve_remote, validate_open_timeouts},
     socket_options::{apply_dscp_to_socket, clear_dscp_on_socket},
     timing::ClientTimestamp,
 };
 
-const MAX_OPEN_PACKET_SIZE: usize = 512;
-const MIN_RECV_BUFFER_SIZE: usize = 2048;
+#[cfg(test)]
+use crate::{
+    runtime::{
+        compute_one_way, compute_rtt, params_from_config, sequence_is_after, sequence_is_before,
+        unix_epoch_ns_i64, update_highest_received,
+    },
+    session::negotiate_params,
+    NegotiatedParams, RunMode, SignedDuration, WarningKind, MAX_UDP_PAYLOAD_LENGTH,
+};
 
 /// Low-level synchronous IRTT client.
 ///
@@ -40,13 +36,9 @@ const MIN_RECV_BUFFER_SIZE: usize = 2048;
 /// instead.
 #[derive(Debug)]
 pub struct Client {
-    config: ClientConfig,
+    runtime: SessionRuntime,
     socket: UdpSocket,
     remote: SocketAddr,
-    requested: Params,
-    negotiated: Option<NegotiatedParams>,
-    phase: ClientPhase,
-    session: Option<ActiveSession>,
     recv_buffer: Vec<u8>,
 }
 
@@ -58,29 +50,15 @@ impl Client {
     /// IRTT open exchange.
     pub fn connect(config: ClientConfig) -> Result<Self, ClientError> {
         validate_open_timeouts(&config.open_timeouts)?;
-        if config.max_pending_probes == 0 {
-            return Err(ClientError::InvalidConfig {
-                reason: "max_pending_probes must be greater than zero".to_owned(),
-            });
-        }
-        if config.probe_timeout == Duration::ZERO {
-            return Err(ClientError::InvalidConfig {
-                reason: "probe_timeout must be greater than zero".to_owned(),
-            });
-        }
         let remote = resolve_remote(&config)?;
+        let runtime = SessionRuntime::new(config.clone(), remote)?;
         let socket = connect_udp_socket(&config.socket_config, remote)?;
-        let requested = params_from_config(&config)?;
 
         Ok(Self {
-            config,
+            runtime,
             socket,
             remote,
-            requested,
-            negotiated: None,
-            phase: ClientPhase::Connected,
-            session: None,
-            recv_buffer: vec![0_u8; MIN_RECV_BUFFER_SIZE],
+            recv_buffer: vec![0_u8; recv_buffer_size(false, None)?],
         })
     }
 
@@ -90,34 +68,37 @@ impl Client {
     /// client into either an open probe session or completed no-test state.
     /// Open attempts use [`ClientConfig::open_timeouts`].
     pub fn open(&mut self) -> Result<OpenOutcome, ClientError> {
-        match self.phase {
-            ClientPhase::Connected => {}
-            ClientPhase::Open { .. } => return Err(ClientError::AlreadyOpen),
-            ClientPhase::Closed => return Err(ClientError::AlreadyClosed),
-            ClientPhase::NoTestCompleted => return Err(ClientError::AlreadyCompleted),
-        }
-
         let outcome = (|| -> Result<OpenOutcome, ClientError> {
-            let request = OpenRequest {
-                params: self.requested.clone(),
-                close: self.config.run_mode == RunMode::NoTest,
-            };
-
-            let packet = encode_open_request(&request, self.config.hmac_key.as_deref())?;
+            let packet = self.runtime.open_packet()?;
             let mut buf = [0_u8; MAX_OPEN_PACKET_SIZE];
 
-            for timeout in &self.config.open_timeouts {
+            for timeout in &self.runtime.config().open_timeouts {
                 self.socket.set_read_timeout(Some(*timeout))?;
                 self.socket.send(&packet)?;
 
                 match self.socket.recv(&mut buf) {
                     Ok(size) => {
-                        let reply = irtt_proto::decode_open_reply(
-                            &buf[..size],
-                            self.config.hmac_key.as_deref(),
-                        )?;
+                        let reply = self.runtime.decode_open_reply(&buf[..size])?;
+                        let remote = self.remote;
+                        let has_hmac = self.runtime.has_hmac();
+                        let socket = &self.socket;
+                        let recv_buffer = &mut self.recv_buffer;
 
-                        return self.accept_open_reply(reply, ClientTimestamp::now());
+                        return self.runtime.accept_open_reply(
+                            reply,
+                            ClientTimestamp::now(),
+                            |negotiated| {
+                                let size = recv_buffer_size(has_hmac, Some(negotiated))?;
+                                let negotiated_dscp = u8::try_from(negotiated.params.dscp)
+                                    .map_err(|_| ClientError::InvalidConfig {
+                                        reason: "negotiated dscp must be in range 0..=63"
+                                            .to_owned(),
+                                    })?;
+                                apply_dscp_to_socket(socket, remote, negotiated_dscp)?;
+                                recv_buffer.resize(size, 0);
+                                Ok(())
+                            },
+                        );
                     }
                     Err(err)
                         if matches!(
@@ -133,7 +114,7 @@ impl Client {
 
         let restore = self
             .socket
-            .set_read_timeout(self.config.socket_config.recv_timeout);
+            .set_read_timeout(self.runtime.config().socket_config.recv_timeout);
 
         match (outcome, restore) {
             (Ok(outcome), Ok(())) => Ok(outcome),
@@ -148,44 +129,24 @@ impl Client {
     /// The close event means the client has sent its close packet and stopped
     /// tracking the session locally; it is not a server acknowledgement.
     pub fn close(&mut self) -> Result<Vec<ClientEvent>, ClientError> {
-        let token = match self.phase {
-            ClientPhase::Open { token } => token,
-            ClientPhase::Closed => return Err(ClientError::AlreadyClosed),
-            ClientPhase::Connected | ClientPhase::NoTestCompleted => {
-                return Err(ClientError::NotOpen)
-            }
-        };
-
-        clear_dscp_on_socket(&self.socket, self.remote)?;
-        let packet =
-            encode_close_request(&CloseRequest { token }, self.config.hmac_key.as_deref())?;
-        self.socket.send(&packet)?;
-        self.phase = ClientPhase::Closed;
-        if let Some(session) = self.session.as_mut() {
-            session.timed_out.clear();
-        }
-        self.session = None;
-
-        Ok(vec![ClientEvent::SessionClosed {
-            remote: self.remote,
-            token,
-            at: ClientTimestamp::now(),
-        }])
+        let socket = &self.socket;
+        let remote = self.remote;
+        self.runtime.close_with(|packet| {
+            clear_dscp_on_socket(socket, remote)?;
+            socket.send(packet)?;
+            Ok(())
+        })
     }
 
     /// Return the monotonic deadline for the next probe send, if another probe
     /// is scheduled.
     pub fn next_send_deadline(&self) -> Option<Instant> {
-        let session = self.session.as_ref()?;
-        if session.sending_done {
-            return None;
-        }
-        Some(session.next_send_at)
+        self.runtime.next_send_deadline()
     }
 
     /// Return the local timeout used to classify pending probes as lost.
     pub fn probe_timeout(&self) -> Duration {
-        self.config.probe_timeout
+        self.runtime.probe_timeout()
     }
 
     /// Send one echo probe if the negotiated run is still active.
@@ -202,126 +163,6 @@ impl Client {
     /// Returns an empty event list when the socket read would block or times
     /// out. Malformed or unrelated datagrams are reported as warning events.
     pub fn recv_once(&mut self) -> Result<Vec<ClientEvent>, ClientError> {
-        self.recv_once_inner(None)
-    }
-
-    fn send_probe_inner(
-        &mut self,
-        override_ts: Option<ClientTimestamp>,
-    ) -> Result<Vec<ClientEvent>, ClientError> {
-        let token = match self.phase {
-            ClientPhase::Open { token } => token,
-            ClientPhase::Closed => return Err(ClientError::AlreadyClosed),
-            ClientPhase::Connected => return Err(ClientError::NotOpen),
-            ClientPhase::NoTestCompleted => return Err(ClientError::AlreadyCompleted),
-        };
-
-        let session = self
-            .session
-            .as_mut()
-            .expect("session must exist when phase is Open");
-
-        if session.sending_done {
-            return Ok(vec![]);
-        }
-
-        let now = override_ts.unwrap_or_else(ClientTimestamp::now);
-
-        if let Some(end) = session.end_mono {
-            if now.mono >= end {
-                session.sending_done = true;
-                return Ok(vec![]);
-            }
-        }
-
-        session.pending.check_capacity()?;
-
-        let negotiated = self
-            .negotiated
-            .as_ref()
-            .expect("negotiated must exist when Open");
-
-        let wire_seq = session.next_wire_seq;
-        let scheduled_at = session.next_send_at;
-
-        let request = EchoRequest {
-            token,
-            sequence: wire_seq,
-            params: negotiated.params.clone(),
-            payload: vec![],
-        };
-        let packet = encode_echo_request(&request, self.config.hmac_key.as_deref())?;
-        let sent_at = override_ts.unwrap_or_else(ClientTimestamp::now);
-        let send_call_start = Instant::now();
-        let bytes = self.socket.send(&packet)?;
-        let send_call = send_call_start.elapsed();
-        let timer_error = instant_abs_diff(sent_at.mono, scheduled_at);
-
-        let session = self
-            .session
-            .as_mut()
-            .expect("session must exist when phase is Open");
-
-        let pending = PendingProbe {
-            wire_seq,
-            sent_at,
-            timeout_at: sent_at
-                .mono
-                .checked_add(self.config.probe_timeout)
-                .ok_or(ClientError::DurationOverflow)?,
-        };
-        session.pending.insert(pending)?;
-
-        session.next_wire_seq = session.next_wire_seq.wrapping_add(1);
-        session.packets_sent =
-            session
-                .packets_sent
-                .checked_add(1)
-                .ok_or(ClientError::CounterOverflow {
-                    counter: "packets_sent",
-                })?;
-
-        let negotiated = self
-            .negotiated
-            .as_ref()
-            .expect("negotiated must exist when Open");
-        let interval_ns = u64::try_from(negotiated.params.interval_ns)
-            .expect("validated positive negotiated interval");
-        let session = self
-            .session
-            .as_mut()
-            .expect("session must exist when phase is Open");
-        session.next_send_at =
-            next_probe_deadline(session.start_mono, interval_ns, session.packets_sent)?;
-
-        if let Some(end) = session.end_mono {
-            if session.next_send_at >= end {
-                session.sending_done = true;
-            }
-        }
-
-        Ok(vec![ClientEvent::EchoSent {
-            seq: wire_seq,
-            remote: self.remote,
-            scheduled_at,
-            sent_at,
-            bytes,
-            send_call,
-            timer_error,
-        }])
-    }
-
-    fn recv_once_inner(
-        &mut self,
-        override_ts: Option<ClientTimestamp>,
-    ) -> Result<Vec<ClientEvent>, ClientError> {
-        match self.phase {
-            ClientPhase::Open { .. } => {}
-            ClientPhase::Closed => return Err(ClientError::AlreadyClosed),
-            ClientPhase::Connected => return Err(ClientError::NotOpen),
-            ClientPhase::NoTestCompleted => return Err(ClientError::AlreadyCompleted),
-        }
-
         let datagram = match recv_datagram(&self.socket, &mut self.recv_buffer) {
             Ok(datagram) => datagram,
             Err(err)
@@ -335,16 +176,11 @@ impl Client {
             Err(err) => return Err(ClientError::Socket(err)),
         };
 
-        let now = override_ts.unwrap_or(datagram.received_at);
-        let packet_len = datagram.len;
-        let Some(reply) = self.decode_received_packet(&self.recv_buffer[..packet_len]) else {
-            return Ok(vec![ClientEvent::Warning {
-                kind: WarningKind::MalformedOrUnrelatedPacket,
-                message: "dropped malformed or unrelated packet".to_owned(),
-                at: now,
-            }]);
-        };
-        self.process_echo_reply(reply, packet_len, now, datagram.meta)
+        self.runtime.process_received_echo_packet(
+            &self.recv_buffer[..datagram.len],
+            datagram.received_at,
+            datagram.meta,
+        )
     }
 
     /// Receive and classify datagrams until a receive produces no events or the
@@ -357,6 +193,9 @@ impl Client {
                 break;
             }
             all_events.extend(events);
+            if self.is_peer_closed() {
+                break;
+            }
         }
         Ok(all_events)
     }
@@ -374,30 +213,7 @@ impl Client {
     ///
     /// `now` is monotonic time only; wall-clock time is not used for timeout expiry.
     pub fn poll_timeouts_at(&mut self, now: Instant) -> Result<Vec<ClientEvent>, ClientError> {
-        match self.phase {
-            ClientPhase::Open { .. } => {}
-            ClientPhase::Closed => return Err(ClientError::AlreadyClosed),
-            ClientPhase::Connected => return Err(ClientError::NotOpen),
-            ClientPhase::NoTestCompleted => return Err(ClientError::AlreadyCompleted),
-        }
-
-        let session = self
-            .session
-            .as_mut()
-            .expect("session must exist when phase is Open");
-
-        let expired = session.pending.drain_expired(now);
-        let mut events = Vec::with_capacity(expired.len());
-        for probe in expired {
-            events.push(ClientEvent::EchoLoss {
-                seq: probe.wire_seq,
-                sent_at: probe.sent_at,
-                timeout_at: probe.timeout_at,
-            });
-            session.timed_out.insert(probe);
-        }
-
-        Ok(events)
+        self.runtime.poll_timeouts_at(now)
     }
 
     /// Return whether the current run has completed.
@@ -406,294 +222,42 @@ impl Client {
     /// pending probes have either replied or timed out. No-test and closed
     /// sessions are also considered complete.
     pub fn is_run_complete(&self) -> bool {
-        let Some(session) = self.session.as_ref() else {
-            return matches!(
-                self.phase,
-                ClientPhase::Closed | ClientPhase::NoTestCompleted
-            );
-        };
-        session.sending_done && session.pending.len() == 0
+        self.runtime.is_run_complete()
+    }
+
+    /// Return whether the session was closed by a peer close-flagged reply.
+    ///
+    /// Direct operations on a closed client still return
+    /// [`ClientError::AlreadyClosed`]. This method lets higher-level run loops
+    /// avoid treating a successfully observed peer close as a local cleanup
+    /// failure.
+    pub fn is_peer_closed(&self) -> bool {
+        self.runtime.is_peer_closed()
     }
 
     pub(crate) fn has_timed_out_metadata(&self) -> bool {
-        self.session
-            .as_ref()
-            .is_some_and(|session| session.timed_out.len() > 0)
+        self.runtime.has_timed_out_metadata()
     }
 
     pub(crate) fn packets_sent(&self) -> u64 {
-        self.session
-            .as_ref()
-            .map_or(0, |session| session.packets_sent)
+        self.runtime.packets_sent()
     }
 
-    fn decode_received_packet(&self, packet: &[u8]) -> Option<EchoReply> {
-        let negotiated = self
-            .negotiated
-            .as_ref()
-            .expect("negotiated must exist when Open");
-
-        decode_echo_reply(packet, &negotiated.params, self.config.hmac_key.as_deref()).ok()
-    }
-
-    fn process_echo_reply(
+    fn send_probe_inner(
         &mut self,
-        reply: EchoReply,
-        packet_len: usize,
-        now: ClientTimestamp,
-        meta: ReceiveMeta,
+        override_ts: Option<ClientTimestamp>,
     ) -> Result<Vec<ClientEvent>, ClientError> {
-        let token = match self.phase {
-            ClientPhase::Open { token } => token,
-            _ => unreachable!(),
-        };
-        if reply.token != token {
-            return Ok(vec![ClientEvent::Warning {
-                kind: WarningKind::WrongToken,
-                message: format!(
-                    "dropped reply with wrong token: expected {token:#x}, got {:#x}",
-                    reply.token
-                ),
-                at: now,
-            }]);
-        }
-
-        let session = self.session.as_mut().expect("session must exist when Open");
-
-        let wire_seq = reply.sequence;
-
-        if let Some(pending) = session.pending.remove(wire_seq) {
-            let rtt = compute_rtt(&pending.sent_at, &now, &reply.timestamps);
-            let server_timing = build_server_timing(&reply.timestamps);
-            let one_way = compute_one_way(&pending.sent_at, &now, &reply.timestamps);
-            let received_stats = build_received_stats(&reply);
-            let is_late = session
-                .highest_received_seq
-                .is_some_and(|h| sequence_is_before(wire_seq, h));
-            let highest_seen = session.highest_received_seq.unwrap_or(wire_seq);
-
-            update_highest_received(&mut session.highest_received_seq, wire_seq);
-            session.completed.insert(wire_seq);
-
-            let mut events = Vec::new();
-            if is_late {
-                events.push(ClientEvent::LateReply {
-                    seq: wire_seq,
-                    highest_seen,
-                    remote: self.remote,
-                    sent_at: Some(pending.sent_at),
-                    received_at: now,
-                    rtt: Some(rtt),
-                    server_timing,
-                    one_way,
-                    received_stats,
-                    bytes: packet_len,
-                    packet_meta: meta.into(),
-                });
-            } else {
-                events.push(ClientEvent::EchoReply {
-                    seq: wire_seq,
-                    remote: self.remote,
-                    sent_at: pending.sent_at,
-                    received_at: now,
-                    rtt,
-                    server_timing,
-                    one_way,
-                    received_stats,
-                    bytes: packet_len,
-                    packet_meta: meta.into(),
-                });
-            }
-            if flags::has(reply.flags, flags::FLAG_CLOSE) {
-                self.close_from_peer(token, now, &mut events)?;
-            }
-            Ok(events)
-        } else if session.completed.contains(wire_seq) {
-            update_highest_received(&mut session.highest_received_seq, wire_seq);
-            Ok(vec![ClientEvent::DuplicateReply {
-                seq: wire_seq,
-                remote: self.remote,
-                received_at: now,
-                bytes: packet_len,
-            }])
-        } else if let Some(timed_out) = session.timed_out.remove(wire_seq) {
-            let rtt = compute_rtt(&timed_out.sent_at, &now, &reply.timestamps);
-            let server_timing = build_server_timing(&reply.timestamps);
-            let one_way = compute_one_way(&timed_out.sent_at, &now, &reply.timestamps);
-            let received_stats = build_received_stats(&reply);
-            let highest_seen = session.highest_received_seq.unwrap_or(wire_seq);
-            update_highest_received(&mut session.highest_received_seq, wire_seq);
-            session.completed.insert(wire_seq);
-
-            let mut events = vec![ClientEvent::LateReply {
-                seq: wire_seq,
-                highest_seen,
-                remote: self.remote,
-                sent_at: Some(timed_out.sent_at),
-                received_at: now,
-                rtt: Some(rtt),
-                server_timing,
-                one_way,
-                received_stats,
-                bytes: packet_len,
-                packet_meta: meta.into(),
-            }];
-            if flags::has(reply.flags, flags::FLAG_CLOSE) {
-                self.close_from_peer(token, now, &mut events)?;
-            }
-            Ok(events)
-        } else if session
-            .highest_received_seq
-            .is_some_and(|h| sequence_is_before(wire_seq, h))
-        {
-            Ok(vec![ClientEvent::LateReply {
-                seq: wire_seq,
-                highest_seen: session.highest_received_seq.unwrap(),
-                remote: self.remote,
-                sent_at: None,
-                received_at: now,
-                rtt: None,
-                server_timing: build_server_timing(&reply.timestamps),
-                one_way: None,
-                received_stats: build_received_stats(&reply),
-                bytes: packet_len,
-                packet_meta: meta.into(),
-            }])
-        } else {
-            Ok(vec![ClientEvent::Warning {
-                kind: WarningKind::UntrackedReply,
-                message: format!(
-                    "dropped reply with untracked seq {wire_seq} (no pending or completed entry)"
-                ),
-                at: now,
-            }])
-        }
-    }
-
-    fn close_from_peer(
-        &mut self,
-        token: u64,
-        now: ClientTimestamp,
-        events: &mut Vec<ClientEvent>,
-    ) -> Result<(), ClientError> {
-        clear_dscp_on_socket(&self.socket, self.remote)?;
-        self.phase = ClientPhase::Closed;
-        if let Some(session) = self.session.as_mut() {
-            session.timed_out.clear();
-        }
-        self.session = None;
-        events.push(ClientEvent::SessionClosed {
-            remote: self.remote,
-            token,
-            at: now,
-        });
-        Ok(())
-    }
-
-    fn accept_open_reply(
-        &mut self,
-        reply: OpenReply,
-        now: ClientTimestamp,
-    ) -> Result<OpenOutcome, ClientError> {
-        if reply.params.protocol_version != PROTOCOL_VERSION {
-            return Err(ClientError::ProtocolVersionMismatch {
-                requested: PROTOCOL_VERSION,
-                received: reply.params.protocol_version,
-            });
-        }
-
-        let reply_is_close = flags::has(reply.flags, flags::FLAG_CLOSE);
-        match self.config.run_mode {
-            RunMode::Normal if reply_is_close => Err(ClientError::ServerRejected),
-            RunMode::Normal if reply.token == 0 => Err(ClientError::ZeroToken),
-            RunMode::Normal => self.accept_normal_open(reply, now),
-            RunMode::NoTest if !reply_is_close => Err(ClientError::UnexpectedNoTestReply),
-            RunMode::NoTest if reply.token != 0 => {
-                Err(ClientError::NonZeroNoTestToken { token: reply.token })
-            }
-            RunMode::NoTest => self.accept_no_test_open(reply, now),
-        }
-    }
-
-    fn accept_normal_open(
-        &mut self,
-        reply: OpenReply,
-        now: ClientTimestamp,
-    ) -> Result<OpenOutcome, ClientError> {
-        let token = reply.token;
-        let negotiated = negotiate_params(
-            &self.requested,
-            reply.params,
-            self.config.negotiation_policy,
-        )?;
-        let recv_buffer_size = recv_buffer_size(self.config.hmac_key.is_some(), Some(&negotiated))?;
-        let negotiated_dscp =
-            u8::try_from(negotiated.params.dscp).map_err(|_| ClientError::InvalidConfig {
-                reason: "negotiated dscp must be in range 0..=63".to_owned(),
-            })?;
-        apply_dscp_to_socket(&self.socket, self.remote, negotiated_dscp)?;
-        self.negotiated = Some(negotiated.clone());
-        self.recv_buffer.resize(recv_buffer_size, 0);
-        self.phase = ClientPhase::Open { token };
-
-        let end_mono = if negotiated.params.duration_ns > 0 {
-            Some(negotiated_end_mono(
-                now.mono,
-                negotiated.params.duration_ns,
-            )?)
-        } else {
-            None
-        };
-
-        self.session = Some(ActiveSession {
-            next_wire_seq: 0,
-            highest_received_seq: None,
-            packets_sent: 0,
-            start_mono: now.mono,
-            end_mono,
-            next_send_at: now.mono,
-            pending: PendingMap::new(self.config.max_pending_probes),
-            timed_out: TimedOutMap::new(self.config.max_pending_probes),
-            completed: CompletedSet::new(self.config.max_pending_probes),
-            sending_done: false,
-        });
-
-        let event = ClientEvent::SessionStarted {
-            remote: self.remote,
-            token,
-            negotiated: negotiated.clone(),
-            at: now,
-        };
-
-        Ok(OpenOutcome::Started {
-            remote: self.remote,
-            token,
-            negotiated,
-            event,
+        let socket = &self.socket;
+        self.runtime.send_probe_with(override_ts, |packet| {
+            let sent_at = override_ts.unwrap_or_else(ClientTimestamp::now);
+            let send_call_start = Instant::now();
+            let bytes = socket.send(packet)?;
+            let send_call = send_call_start.elapsed();
+            Ok(SendProbeResult {
+                sent_at,
+                bytes,
+                send_call,
             })
-    }
-
-    fn accept_no_test_open(
-        &mut self,
-        reply: OpenReply,
-        now: ClientTimestamp,
-    ) -> Result<OpenOutcome, ClientError> {
-        let negotiated = negotiate_params(
-            &self.requested,
-            reply.params,
-            self.config.negotiation_policy,
-        )?;
-        self.negotiated = Some(negotiated.clone());
-        self.phase = ClientPhase::NoTestCompleted;
-        let event = ClientEvent::NoTestCompleted {
-            remote: self.remote,
-            negotiated: negotiated.clone(),
-            at: now,
-        };
-        Ok(OpenOutcome::NoTestCompleted {
-            remote: self.remote,
-            negotiated,
-            event,
         })
     }
 }
@@ -705,233 +269,5 @@ impl Client {
     }
 }
 
-fn update_highest_received(highest_received_seq: &mut Option<u32>, wire_seq: u32) {
-    *highest_received_seq = Some(highest_received_seq.map_or(wire_seq, |h| {
-        if sequence_is_after(wire_seq, h) {
-            wire_seq
-        } else {
-            h
-        }
-    }));
-}
-
-fn next_probe_deadline(
-    start: Instant,
-    interval_ns: u64,
-    packets_sent: u64,
-) -> Result<Instant, ClientError> {
-    let offset_ns = interval_ns
-        .checked_mul(packets_sent)
-        .ok_or(ClientError::DurationOverflow)?;
-    start
-        .checked_add(Duration::from_nanos(offset_ns))
-        .ok_or(ClientError::DurationOverflow)
-}
-
-fn sequence_is_after(candidate: u32, current: u32) -> bool {
-    candidate != current && candidate.wrapping_sub(current) < (1 << 31)
-}
-
-fn sequence_is_before(candidate: u32, current: u32) -> bool {
-    current != candidate && current.wrapping_sub(candidate) < (1 << 31)
-}
-
-fn instant_abs_diff(left: Instant, right: Instant) -> Duration {
-    left.checked_duration_since(right)
-        .or_else(|| right.checked_duration_since(left))
-        .unwrap_or(Duration::ZERO)
-}
-
-pub(crate) fn recv_buffer_size(
-    has_hmac: bool,
-    negotiated: Option<&NegotiatedParams>,
-) -> Result<usize, ClientError> {
-    Ok(match negotiated {
-        Some(negotiated) => echo_packet_len(has_hmac, &negotiated.params)?
-            .saturating_add(1)
-            .max(MIN_RECV_BUFFER_SIZE),
-        None => MIN_RECV_BUFFER_SIZE,
-    })
-}
-
-fn compute_rtt(
-    sent_at: &ClientTimestamp,
-    received_at: &ClientTimestamp,
-    ts: &TimestampFields,
-) -> RttSample {
-    let raw = received_at
-        .mono
-        .checked_duration_since(sent_at.mono)
-        .unwrap_or(Duration::ZERO);
-
-    let server_processing = compute_server_processing(ts);
-
-    let adjusted = server_processing
-        .map(|sp| SignedDuration::from_nanos(duration_ns_i128(raw) - duration_ns_i128(sp)));
-    let effective = adjusted.unwrap_or_else(|| SignedDuration::from_duration(raw));
-
-    RttSample {
-        raw,
-        adjusted,
-        effective,
-    }
-}
-
-fn duration_ns_i128(duration: Duration) -> i128 {
-    i128::try_from(duration.as_nanos()).unwrap_or(i128::MAX)
-}
-
-fn compute_server_processing(ts: &TimestampFields) -> Option<Duration> {
-    if let (Some(recv_mono), Some(send_mono)) = (ts.recv_mono, ts.send_mono) {
-        let diff = send_mono.checked_sub(recv_mono)?;
-        return Some(Duration::from_nanos(u64::try_from(diff).ok()?));
-    }
-    if let (Some(recv_wall), Some(send_wall)) = (ts.recv_wall, ts.send_wall) {
-        let diff = send_wall.checked_sub(recv_wall)?;
-        return Some(Duration::from_nanos(u64::try_from(diff).ok()?));
-    }
-    None
-}
-
-fn build_server_timing(ts: &TimestampFields) -> Option<ServerTiming> {
-    if ts.recv_wall.is_none()
-        && ts.recv_mono.is_none()
-        && ts.send_wall.is_none()
-        && ts.send_mono.is_none()
-        && ts.midpoint_wall.is_none()
-        && ts.midpoint_mono.is_none()
-    {
-        return None;
-    }
-    Some(ServerTiming {
-        receive_wall_ns: ts.recv_wall,
-        receive_mono_ns: ts.recv_mono,
-        send_wall_ns: ts.send_wall,
-        send_mono_ns: ts.send_mono,
-        midpoint_wall_ns: ts.midpoint_wall,
-        midpoint_mono_ns: ts.midpoint_mono,
-        processing: compute_server_processing(ts),
-    })
-}
-
-fn compute_one_way(
-    sent_at: &ClientTimestamp,
-    received_at: &ClientTimestamp,
-    ts: &TimestampFields,
-) -> Option<OneWayDelaySample> {
-    let server_recv_wall = ts.recv_wall.or(ts.midpoint_wall);
-    let server_send_wall = ts.send_wall.or(ts.midpoint_wall);
-
-    let client_send_ns = unix_epoch_ns_i64(sent_at.wall);
-    let client_recv_ns = unix_epoch_ns_i64(received_at.wall);
-
-    let c2s = server_recv_wall
-        .zip(client_send_ns)
-        .and_then(|(srv, cli)| srv.checked_sub(cli))
-        .map(|d| SignedDuration::from_nanos(i128::from(d)));
-    let s2c = client_recv_ns
-        .zip(server_send_wall)
-        .and_then(|(cli, srv)| cli.checked_sub(srv))
-        .map(|d| SignedDuration::from_nanos(i128::from(d)));
-
-    if c2s.is_none() && s2c.is_none() {
-        return None;
-    }
-
-    Some(OneWayDelaySample {
-        client_to_server: c2s,
-        server_to_client: s2c,
-    })
-}
-
-fn unix_epoch_ns_i64(time: SystemTime) -> Option<i64> {
-    time.duration_since(UNIX_EPOCH)
-        .ok()
-        .and_then(|duration| i64::try_from(duration.as_nanos()).ok())
-}
-
-fn build_received_stats(reply: &EchoReply) -> Option<ReceivedStatsSample> {
-    if reply.recv_count.is_none() && reply.recv_window.is_none() {
-        return None;
-    }
-    Some(ReceivedStatsSample {
-        count: reply.recv_count,
-        window: reply.recv_window,
-    })
-}
-
-fn params_from_config(config: &ClientConfig) -> Result<Params, ClientError> {
-    validate_protocol_config(config)?;
-    Ok(Params {
-        protocol_version: PROTOCOL_VERSION,
-        duration_ns: match config.duration {
-            Some(duration) => config_duration_to_ns("duration", duration)?,
-            None => 0,
-        },
-        interval_ns: config_duration_to_ns("interval", config.interval)?,
-        length: i64::from(config.length),
-        received_stats: config.received_stats,
-        stamp_at: config.stamp_at,
-        clock: config.clock,
-        dscp: i64::from(config.dscp),
-        server_fill: config.server_fill.clone().map(|value| ServerFill { value }),
-    })
-}
-
-fn validate_protocol_config(config: &ClientConfig) -> Result<(), ClientError> {
-    if config.duration == Some(Duration::ZERO) {
-        return Err(ClientError::InvalidConfig {
-            reason: "duration must be greater than zero; use None for continuous mode".to_owned(),
-        });
-    }
-    if config.interval == Duration::ZERO {
-        return Err(ClientError::InvalidConfig {
-            reason: "interval must be greater than zero".to_owned(),
-        });
-    }
-    if config.dscp > MAX_DSCP_CODEPOINT {
-        return Err(ClientError::InvalidConfig {
-            reason: format!("dscp must be <= {MAX_DSCP_CODEPOINT}"),
-        });
-    }
-    if config.length > MAX_UDP_PAYLOAD_LENGTH {
-        return Err(ClientError::InvalidConfig {
-            reason: format!("packet length must be <= {MAX_UDP_PAYLOAD_LENGTH}"),
-        });
-    }
-
-    if let Some(fill) = &config.server_fill {
-        let len = fill.len();
-        if len == 0 {
-            return Err(ClientError::InvalidConfig {
-                reason: "server_fill must not be empty".to_owned(),
-            });
-        }
-        if len > MAX_SERVER_FILL_BYTES {
-            return Err(ClientError::InvalidConfig {
-                reason: format!("server_fill must be <= {MAX_SERVER_FILL_BYTES} bytes, got {len}"),
-            });
-        }
-    }
-
-    Ok(())
-}
-
-fn config_duration_to_ns(field: &str, duration: Duration) -> Result<i64, ClientError> {
-    i64::try_from(duration.as_nanos()).map_err(|_| ClientError::InvalidConfig {
-        reason: format!("{field} is too large to encode as nanoseconds"),
-    })
-}
-
-fn negotiated_end_mono(start: Instant, duration_ns: i64) -> Result<Instant, ClientError> {
-    debug_assert!(duration_ns > 0);
-    let duration_ns = u64::try_from(duration_ns).expect("validated positive negotiated duration");
-    start
-        .checked_add(Duration::from_nanos(duration_ns))
-        .ok_or_else(|| ClientError::NegotiationRejected {
-            reason: "duration is too large to schedule".to_owned(),
-        })
-}
-
 #[cfg(test)]
 mod tests;

crates/irtt-client/src/config.rs

@@ -118,6 +118,30 @@ pub struct ClientConfig {
     pub max_pending_probes: usize,
 }
 
+/// Authentication settings used by client sessions.
+///
+/// `ClientConfig` keeps its existing top-level HMAC field for source
+/// compatibility. Managed multi-target callers can use this smaller type for
+/// per-target auth overrides without carrying a full independent
+/// [`ClientConfig`].
+#[derive(Debug, Clone, PartialEq, Eq, Default)]
+pub struct ClientAuthConfig {
+    /// Optional HMAC key used to authenticate IRTT packets.
+    pub hmac_key: Option<Vec<u8>>,
+}
+
+impl From<Option<Vec<u8>>> for ClientAuthConfig {
+    fn from(hmac_key: Option<Vec<u8>>) -> Self {
+        Self { hmac_key }
+    }
+}
+
+impl From<ClientAuthConfig> for Option<Vec<u8>> {
+    fn from(auth: ClientAuthConfig) -> Self {
+        auth.hmac_key
+    }
+}
+
 impl Default for ClientConfig {
     fn default() -> Self {
         Self {

crates/irtt-client/src/lib.rs

@@ -59,6 +59,7 @@ mod managed;
 mod metadata;
 mod probe;
 mod receive;
+mod runtime;
 mod session;
 mod socket;
 mod socket_options;
@@ -66,8 +67,8 @@ mod timing;
 
 pub use client::Client;
 pub use config::{
-    ClientConfig, NegotiationPolicy, RecvBudget, RunMode, SocketConfig, MAX_DSCP_CODEPOINT,
-    MAX_SERVER_FILL_BYTES, MAX_TTL, MAX_UDP_PAYLOAD_LENGTH,
+    ClientAuthConfig, ClientConfig, NegotiationPolicy, RecvBudget, RunMode, SocketConfig,
+    MAX_DSCP_CODEPOINT, MAX_SERVER_FILL_BYTES, MAX_TTL, MAX_UDP_PAYLOAD_LENGTH,
 };
 pub use error::{ClientError, EventSubscriptionError};
 pub use event::{
@@ -75,8 +76,11 @@ pub use event::{
     ServerTiming, SignedDuration, WarningKind,
 };
 pub use managed::{
-    CancellationToken, EventHub, EventSubscription, ManagedClient, ManagedClientSession,
-    SessionEndReason, SessionOutcome, SubscriberConfig, SubscriberOverflow,
+    CancellationToken, EventHub, EventSubscription, ManagedClient, ManagedClientGroup,
+    ManagedClientGroupConfig, ManagedClientGroupSession, ManagedClientSession,
+    ManagedGroupEndReason, ManagedGroupOutcome, ManagedGroupPacing, ManagedTargetConfig,
+    ManagedTargetEndReason, ManagedTargetOutcome, SessionEndReason, SessionOutcome,
+    SubscriberConfig, SubscriberOverflow, TargetEvent, TargetEventSubscription, TargetId,
 };
 pub use session::{NegotiatedParams, NegotiationRestriction};
 pub use timing::ClientTimestamp;

crates/irtt-client/src/managed/hub.rs

@@ -45,20 +45,20 @@ pub enum SubscriberOverflow {
     Disconnect,
 }
 
-/// Publish/subscribe fan-out for [`ClientEvent`] values.
+/// Publish/subscribe fan-out for managed event values.
 ///
 /// `EventHub` is used by managed sessions internally and is also exported for
 /// callers that want the same bounded subscription behavior around their own
 /// event producer. Publishing clones each event once per subscriber.
-#[derive(Debug, Clone)]
-pub struct EventHub {
-    inner: Arc<HubInner>,
+#[derive(Debug)]
+pub struct EventHub<T = ClientEvent> {
+    inner: Arc<HubInner<T>>,
 }
 
 #[derive(Debug)]
-struct HubInner {
+struct HubInner<T> {
     next_id: AtomicU64,
-    subscribers: Mutex<HashMap<u64, Arc<SubscriberInner>>>,
+    subscribers: Mutex<HashMap<u64, Arc<SubscriberInner<T>>>>,
 }
 
 /// Handle for receiving managed client events.
@@ -68,26 +68,34 @@ struct HubInner {
 /// when that queue is full. Dropping the handle unregisters the subscriber.
 #[must_use = "dropping the subscription unregisters it"]
 #[derive(Debug)]
-pub struct EventSubscription {
+pub struct EventSubscription<T = ClientEvent> {
     id: u64,
-    hub: Weak<HubInner>,
-    inner: Arc<SubscriberInner>,
+    hub: Weak<HubInner<T>>,
+    inner: Arc<SubscriberInner<T>>,
 }
 
 #[derive(Debug)]
-struct SubscriberInner {
-    state: Mutex<SubscriberState>,
+struct SubscriberInner<T> {
+    state: Mutex<SubscriberState<T>>,
     available: Condvar,
     config: SubscriberConfig,
 }
 
 #[derive(Debug)]
-struct SubscriberState {
-    queue: VecDeque<ClientEvent>,
+struct SubscriberState<T> {
+    queue: VecDeque<T>,
     connected: bool,
 }
 
-impl EventHub {
+impl<T> Clone for EventHub<T> {
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
+        }
+    }
+}
+
+impl<T> EventHub<T> {
     /// Create an empty event hub with no subscribers.
     pub fn new() -> Self {
         Self {
@@ -104,7 +112,7 @@ impl EventHub {
     pub fn subscribe(
         &self,
         config: SubscriberConfig,
-    ) -> Result<EventSubscription, crate::ClientError> {
+    ) -> Result<EventSubscription<T>, crate::ClientError> {
         if config.capacity == 0 {
             return Err(crate::ClientError::InvalidConfig {
                 reason: "subscriber capacity must be greater than zero".to_owned(),
@@ -133,13 +141,41 @@ impl EventHub {
         })
     }
 
+    /// Disconnect all subscribers after leaving their already queued events
+    /// available to drain.
+    pub fn disconnect_all(&self) {
+        let subscribers: Vec<Arc<SubscriberInner<T>>> = self
+            .inner
+            .subscribers
+            .lock()
+            .expect("event hub mutex poisoned")
+            .drain()
+            .map(|(_, subscriber)| subscriber)
+            .collect();
+
+        for subscriber in subscribers {
+            subscriber.disconnect();
+        }
+    }
+
+    #[cfg(test)]
+    fn subscriber_count(&self) -> usize {
+        self.inner
+            .subscribers
+            .lock()
+            .expect("event hub mutex poisoned")
+            .len()
+    }
+}
+
+impl<T: Clone> EventHub<T> {
     /// Publish an event to all currently connected subscribers.
     ///
     /// Slow subscribers are handled according to their
     /// [`SubscriberOverflow`] policy. Publishing does not block waiting for a
     /// subscriber to consume queued events.
-    pub fn publish(&self, event: ClientEvent) {
-        let subscribers: Vec<(u64, Arc<SubscriberInner>)> = self
+    pub fn publish(&self, event: T) {
+        let subscribers: Vec<(u64, Arc<SubscriberInner<T>>)> = self
             .inner
             .subscribers
             .lock()
@@ -170,47 +206,21 @@ impl EventHub {
             subscribers.remove(&id);
         }
     }
-
-    /// Disconnect all subscribers after leaving their already queued events
-    /// available to drain.
-    pub fn disconnect_all(&self) {
-        let subscribers: Vec<Arc<SubscriberInner>> = self
-            .inner
-            .subscribers
-            .lock()
-            .expect("event hub mutex poisoned")
-            .drain()
-            .map(|(_, subscriber)| subscriber)
-            .collect();
-
-        for subscriber in subscribers {
-            subscriber.disconnect();
-        }
-    }
-
-    #[cfg(test)]
-    fn subscriber_count(&self) -> usize {
-        self.inner
-            .subscribers
-            .lock()
-            .expect("event hub mutex poisoned")
-            .len()
-    }
 }
 
-impl Default for EventHub {
+impl<T> Default for EventHub<T> {
     fn default() -> Self {
         Self::new()
     }
 }
 
-impl EventSubscription {
+impl<T> EventSubscription<T> {
     /// Block until the next queued event is available.
     ///
     /// If the subscription is disconnected, this returns
     /// [`EventSubscriptionError::Disconnected`] after any already queued events
     /// have been drained.
-    pub fn recv(&self) -> Result<ClientEvent, EventSubscriptionError> {
+    pub fn recv(&self) -> Result<T, EventSubscriptionError> {
         let mut state = self.inner.state.lock().expect("subscriber mutex poisoned");
         loop {
             if let Some(event) = state.queue.pop_front() {
@@ -233,7 +243,7 @@ impl EventSubscription {
     /// is queued. If the subscription is disconnected, this returns
     /// [`EventSubscriptionError::Disconnected`] after any already queued events
     /// have been drained.
-    pub fn try_recv(&self) -> Result<Option<ClientEvent>, EventSubscriptionError> {
+    pub fn try_recv(&self) -> Result<Option<T>, EventSubscriptionError> {
         let mut state = self.inner.state.lock().expect("subscriber mutex poisoned");
         if let Some(event) = state.queue.pop_front() {
             return Ok(Some(event));
@@ -245,7 +255,7 @@ impl EventSubscription {
     }
 }
 
-impl Drop for EventSubscription {
+impl<T> Drop for EventSubscription<T> {
     fn drop(&mut self) {
         self.inner.disconnect();
         if let Some(hub) = self.hub.upgrade() {
@@ -257,8 +267,8 @@ impl Drop for EventSubscription {
     }
 }
 
-impl SubscriberInner {
-    fn publish(&self, event: ClientEvent) -> bool {
+impl<T> SubscriberInner<T> {
+    fn publish(&self, event: T) -> bool {
         let mut state = self.state.lock().expect("subscriber mutex poisoned");
         if !state.connected {
             return false;
@@ -411,7 +421,7 @@ mod tests {
 
     #[test]
     fn dropping_subscription_unregisters_from_hub() {
-        let hub = EventHub::new();
+        let hub: EventHub = EventHub::new();
         let sub = hub.subscribe(SubscriberConfig::default()).unwrap();
         assert_eq!(hub.subscriber_count(), 1);
 
@@ -422,7 +432,7 @@ mod tests {
 
     #[test]
     fn disconnect_all_wakes_blocking_receivers() {
-        let hub = EventHub::new();
+        let hub: EventHub = EventHub::new();
         let sub = hub.subscribe(SubscriberConfig::default()).unwrap();
         hub.disconnect_all();
 

crates/irtt-client/src/managed/mod.rs

@@ -1,7 +1,13 @@
 mod cancellation;
+mod group;
 mod hub;
 mod runner;
 
 pub use cancellation::CancellationToken;
+pub use group::{
+    ManagedClientGroup, ManagedClientGroupConfig, ManagedClientGroupSession, ManagedGroupEndReason,
+    ManagedGroupOutcome, ManagedGroupPacing, ManagedTargetConfig, ManagedTargetEndReason,
+    ManagedTargetOutcome, TargetEvent, TargetEventSubscription, TargetId,
+};
 pub use hub::{EventHub, EventSubscription, SubscriberConfig, SubscriberOverflow};
 pub use runner::{ManagedClient, ManagedClientSession, SessionEndReason, SessionOutcome};

crates/irtt-client/src/managed/runner.rs

@@ -224,7 +224,9 @@ fn run_client(
                 &mut counters,
                 client.recv_available(MANAGED_RECV_BUDGET)?,
             );
+            if !client.is_peer_closed() {
                 publish_events(&hub, &mut counters, client.poll_timeouts()?);
+            }
             break;
         }
 
@@ -243,6 +245,9 @@ fn run_client(
             &mut counters,
             client.recv_available(MANAGED_RECV_BUDGET)?,
         );
+        if client.is_peer_closed() {
+            break;
+        }
         publish_events(&hub, &mut counters, client.poll_timeouts()?);
 
         if client.is_run_complete() {
@@ -257,8 +262,10 @@ fn run_client(
     }
 
     let packets_sent = client.packets_sent();
+    if !client.is_peer_closed() {
         let close_events = client.close()?;
         publish_events(&hub, &mut counters, close_events);
+    }
 
     Ok(SessionOutcome {
         end_reason: if cancelled {
@@ -295,12 +302,20 @@ fn drain_final_late_replies(
 
     let deadline = Instant::now() + MANAGED_FINAL_DRAIN;
     while Instant::now() < deadline && client.has_timed_out_metadata() {
+        if client.is_peer_closed() {
+            break;
+        }
+
         let mut published = false;
 
         let events = client.recv_available(MANAGED_RECV_BUDGET)?;
         published |= !events.is_empty();
         publish_events(hub, counters, events);
 
+        if client.is_peer_closed() {
+            break;
+        }
+
         let events = client.poll_timeouts()?;
         published |= !events.is_empty();
         publish_events(hub, counters, events);
@@ -481,6 +496,53 @@ mod tests {
         FakeServer { addr, done }
     }
 
+    fn start_peer_close_server(params: Params) -> FakeServer {
+        let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+        let addr = socket.local_addr().unwrap();
+        let done = thread::spawn(move || {
+            let (_, peer) = recv_request(&socket);
+            socket
+                .send_to(&open_reply(FLAG_OPEN | FLAG_REPLY, TOKEN, &params), peer)
+                .unwrap();
+            socket
+                .set_read_timeout(Some(Duration::from_millis(500)))
+                .unwrap();
+
+            let Some((packet, peer)) = recv_request_timeout(&socket) else {
+                return;
+            };
+            let seq = u32::from_le_bytes(packet[12..16].try_into().unwrap());
+            let ts = TimestampFields {
+                recv_wall: Some(1_000_000_000),
+                recv_mono: Some(100_000),
+                send_wall: Some(1_000_000_000),
+                send_mono: Some(100_000),
+                ..Default::default()
+            };
+            socket
+                .send_to(
+                    &echo_reply_packet_with_flags(
+                        TOKEN,
+                        seq,
+                        &params,
+                        &ts,
+                        FLAG_REPLY | flags::FLAG_CLOSE,
+                    ),
+                    peer,
+                )
+                .unwrap();
+
+            if let Some((packet, _)) = recv_request_timeout(&socket) {
+                panic!(
+                    "managed cleanup must not send any packet after peer close; flags={:?} len={}",
+                    packet.get(3).copied(),
+                    packet.len()
+                );
+            }
+        });
+        FakeServer { addr, done }
+    }
+
     fn recv_request(socket: &UdpSocket) -> (Vec<u8>, SocketAddr) {
         let mut buf = [0_u8; 2048];
         let (size, peer) = socket.recv_from(&mut buf).unwrap();
@@ -509,13 +571,23 @@ mod tests {
         seq: u32,
         params: &Params,
         timestamps: &TimestampFields,
+    ) -> Vec<u8> {
+        echo_reply_packet_with_flags(token, seq, params, timestamps, FLAG_REPLY)
+    }
+
+    fn echo_reply_packet_with_flags(
+        token: u64,
+        seq: u32,
+        params: &Params,
+        timestamps: &TimestampFields,
+        flags: u8,
     ) -> Vec<u8> {
         let layout = PacketLayout::echo(false, params);
         let packet_len = test_echo_packet_len(false, params);
         let mut packet = Vec::with_capacity(packet_len);
 
         packet.extend_from_slice(&MAGIC);
-        packet.push(FLAG_REPLY);
+        packet.push(flags);
         packet.extend_from_slice(&token.to_le_bytes());
         packet.extend_from_slice(&seq.to_le_bytes());
 
@@ -667,6 +739,31 @@ mod tests {
         assert!(late_before_close < close);
     }
 
+    #[test]
+    fn peer_close_during_managed_run_is_successful() {
+        let server = start_peer_close_server(test_params(None, Duration::from_millis(10)));
+        let (session, sub) = ManagedClient::start_with_subscription(
+            config(server.addr, None),
+            SubscriberConfig {
+                capacity: 16,
+                overflow: SubscriberOverflow::DropNewest,
+            },
+        )
+        .unwrap();
+
+        let events = collect_until_closed(&sub);
+        let outcome = session.join().unwrap();
+        server.join();
+
+        assert_eq!(outcome.end_reason, SessionEndReason::TestComplete);
+        assert!(events
+            .iter()
+            .any(|event| matches!(event, ClientEvent::EchoReply { .. })));
+        assert!(events
+            .iter()
+            .any(|event| matches!(event, ClientEvent::SessionClosed { .. })));
+    }
+
     #[test]
     fn continuous_managed_run_can_be_stopped_cleanly() {
         let server = start_echo_server(test_params(None, Duration::from_millis(10)));

crates/irtt-client/src/receive.rs

@@ -15,6 +15,14 @@ pub(crate) struct ReceivedDatagram {
     pub(crate) meta: ReceiveMeta,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) struct ReceivedDatagramFrom {
+    pub(crate) len: usize,
+    pub(crate) source: SocketAddr,
+    pub(crate) received_at: ClientTimestamp,
+    pub(crate) meta: ReceiveMeta,
+}
+
 #[cfg(not(all(target_os = "linux", feature = "ancillary")))]
 pub(crate) fn recv_datagram(
     socket: &UdpSocket,
@@ -30,6 +38,22 @@ pub(crate) fn recv_datagram(
     })
 }
 
+#[cfg(not(all(target_os = "linux", feature = "ancillary")))]
+pub(crate) fn recv_datagram_from(
+    socket: &UdpSocket,
+    buf: &mut [u8],
+) -> Result<ReceivedDatagramFrom, io::Error> {
+    let (len, source) = socket.recv_from(buf)?;
+    let received_at = ClientTimestamp::now();
+
+    Ok(ReceivedDatagramFrom {
+        len,
+        source,
+        received_at,
+        meta: ReceiveMeta::default(),
+    })
+}
+
 #[cfg(all(target_os = "linux", feature = "ancillary"))]
 pub(crate) fn recv_datagram(
     socket: &UdpSocket,
@@ -38,6 +62,14 @@ pub(crate) fn recv_datagram(
     linux::recv_datagram(socket, buf)
 }
 
+#[cfg(all(target_os = "linux", feature = "ancillary"))]
+pub(crate) fn recv_datagram_from(
+    socket: &UdpSocket,
+    buf: &mut [u8],
+) -> Result<ReceivedDatagramFrom, io::Error> {
+    linux::recv_datagram_from(socket, buf)
+}
+
 #[cfg(not(all(target_os = "linux", feature = "ancillary")))]
 pub(crate) fn configure_receive_metadata(
     _socket: &UdpSocket,

crates/irtt-client/src/receive/linux.rs

@@ -1,13 +1,17 @@
 #![allow(unsafe_code)]
 use std::{
     io, mem,
-    net::{SocketAddr, UdpSocket},
+    net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6, UdpSocket},
     os::fd::AsRawFd,
     ptr,
     time::{Duration, SystemTime, UNIX_EPOCH},
 };
 
-use crate::{metadata::ReceiveMeta, receive::ReceivedDatagram, timing::ClientTimestamp};
+use crate::{
+    metadata::ReceiveMeta,
+    receive::{ReceivedDatagram, ReceivedDatagramFrom},
+    timing::ClientTimestamp,
+};
 
 const CONTROL_LEN: usize = 128;
 
@@ -87,6 +91,61 @@ pub(crate) fn recv_datagram(
     })
 }
 
+pub(crate) fn recv_datagram_from(
+    socket: &UdpSocket,
+    buf: &mut [u8],
+) -> Result<ReceivedDatagramFrom, io::Error> {
+    let mut control = ControlBuffer::new();
+    let mut name: libc::sockaddr_storage = unsafe { mem::zeroed() };
+    let mut iov = libc::iovec {
+        iov_base: buf.as_mut_ptr().cast(),
+        iov_len: buf.len(),
+    };
+    let mut msg: libc::msghdr = unsafe { mem::zeroed() };
+    msg.msg_name = (&mut name as *mut libc::sockaddr_storage).cast();
+    msg.msg_namelen = mem::size_of::<libc::sockaddr_storage>() as libc::socklen_t;
+    msg.msg_iov = &mut iov;
+    msg.msg_iovlen = 1;
+    msg.msg_control = control.as_mut_ptr().cast();
+    msg.msg_controllen = control.len();
+
+    let len = unsafe {
+        // SAFETY: `msg` points to one writable iovec backed by `buf`, a
+        // writable source-address buffer, and a writable control buffer. All
+        // buffers live until `recvmsg` returns. The socket file descriptor is
+        // borrowed from a valid `UdpSocket`.
+        libc::recvmsg(socket.as_raw_fd(), &mut msg, 0)
+    };
+    if len < 0 {
+        return Err(io::Error::last_os_error());
+    }
+    let len = usize::try_from(len).map_err(|_| {
+        io::Error::new(
+            io::ErrorKind::InvalidData,
+            "recvmsg returned an unrepresentable datagram length",
+        )
+    })?;
+    let received_at = ClientTimestamp::now();
+    let source = unsafe {
+        // SAFETY: `name` and `msg_namelen` were initialized by a successful
+        // `recvmsg` call above.
+        socket_addr_from_storage(&name, msg.msg_namelen)?
+    };
+    let meta = unsafe {
+        // SAFETY: `msg` was initialized by a successful `recvmsg` call. The
+        // parser only reads cmsghdr entries within `msg_controllen` and ignores
+        // short or unrelated control messages.
+        parse_receive_meta(&msg)
+    };
+
+    Ok(ReceivedDatagramFrom {
+        len,
+        source,
+        received_at,
+        meta,
+    })
+}
+
 unsafe fn parse_receive_meta(msg: &libc::msghdr) -> ReceiveMeta {
     let mut meta = ReceiveMeta::default();
     let mut cmsg = libc::CMSG_FIRSTHDR(msg);
@@ -108,6 +167,52 @@ unsafe fn parse_receive_meta(msg: &libc::msghdr) -> ReceiveMeta {
     meta
 }
 
+unsafe fn socket_addr_from_storage(
+    storage: &libc::sockaddr_storage,
+    len: libc::socklen_t,
+) -> io::Result<SocketAddr> {
+    match i32::from(storage.ss_family) {
+        libc::AF_INET => {
+            if usize::try_from(len).unwrap_or(0) < mem::size_of::<libc::sockaddr_in>() {
+                return Err(io::Error::new(
+                    io::ErrorKind::InvalidData,
+                    "short IPv4 source address from recvmsg",
+                ));
+            }
+            let addr = ptr::read_unaligned(
+                (storage as *const libc::sockaddr_storage).cast::<libc::sockaddr_in>(),
+            );
+            let ip = Ipv4Addr::from(u32::from_be(addr.sin_addr.s_addr));
+            let port = u16::from_be(addr.sin_port);
+            Ok(SocketAddr::V4(SocketAddrV4::new(ip, port)))
+        }
+        libc::AF_INET6 => {
+            if usize::try_from(len).unwrap_or(0) < mem::size_of::<libc::sockaddr_in6>() {
+                return Err(io::Error::new(
+                    io::ErrorKind::InvalidData,
+                    "short IPv6 source address from recvmsg",
+                ));
+            }
+            let addr = ptr::read_unaligned(
+                (storage as *const libc::sockaddr_storage).cast::<libc::sockaddr_in6>(),
+            );
+            let ip = Ipv6Addr::from(addr.sin6_addr.s6_addr);
+            let port = u16::from_be(addr.sin6_port);
+            let flowinfo = u32::from_be(addr.sin6_flowinfo);
+            Ok(SocketAddr::V6(SocketAddrV6::new(
+                ip,
+                port,
+                flowinfo,
+                addr.sin6_scope_id,
+            )))
+        }
+        family => Err(io::Error::new(
+            io::ErrorKind::InvalidData,
+            format!("unsupported source address family from recvmsg: {family}"),
+        )),
+    }
+}
+
 fn is_traffic_class_cmsg(cmsg: &libc::cmsghdr) -> bool {
     (cmsg.cmsg_level == libc::IPPROTO_IP && cmsg.cmsg_type == libc::IP_TOS)
         || (cmsg.cmsg_level == libc::IPPROTO_IPV6 && cmsg.cmsg_type == libc::IPV6_TCLASS)

crates/irtt-client/src/runtime.rs

@@ -0,0 +1,864 @@
+use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
+
+use irtt_proto::{
+    close::CloseRequest, decode_echo_reply, echo_packet_len, encode_close_request,
+    encode_echo_request, encode_open_request, flags, EchoReply, EchoRequest, OpenReply,
+    OpenRequest, Params, ServerFill, TimestampFields, PROTOCOL_VERSION,
+};
+
+use crate::{
+    config::{
+        ClientConfig, RunMode, MAX_DSCP_CODEPOINT, MAX_SERVER_FILL_BYTES, MAX_UDP_PAYLOAD_LENGTH,
+    },
+    error::ClientError,
+    event::{
+        ClientEvent, OneWayDelaySample, OpenOutcome, ReceivedStatsSample, RttSample, ServerTiming,
+        SignedDuration, WarningKind,
+    },
+    metadata::ReceiveMeta,
+    probe::{CompletedSet, PendingMap, PendingProbe, TimedOutMap},
+    session::{negotiate_params, ActiveSession, ClientPhase, CloseSource, NegotiatedParams},
+    timing::ClientTimestamp,
+};
+
+pub(crate) const MAX_OPEN_PACKET_SIZE: usize = 512;
+const MIN_RECV_BUFFER_SIZE: usize = 2048;
+
+#[derive(Debug)]
+pub(crate) struct SessionRuntime {
+    config: ClientConfig,
+    remote: std::net::SocketAddr,
+    requested: Params,
+    negotiated: Option<NegotiatedParams>,
+    phase: ClientPhase,
+    session: Option<ActiveSession>,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub(crate) struct SendProbeResult {
+    pub(crate) sent_at: ClientTimestamp,
+    pub(crate) bytes: usize,
+    pub(crate) send_call: Duration,
+}
+
+impl SessionRuntime {
+    pub(crate) fn new(
+        config: ClientConfig,
+        remote: std::net::SocketAddr,
+    ) -> Result<Self, ClientError> {
+        if config.max_pending_probes == 0 {
+            return Err(ClientError::InvalidConfig {
+                reason: "max_pending_probes must be greater than zero".to_owned(),
+            });
+        }
+        if config.probe_timeout == Duration::ZERO {
+            return Err(ClientError::InvalidConfig {
+                reason: "probe_timeout must be greater than zero".to_owned(),
+            });
+        }
+        let requested = params_from_config(&config)?;
+
+        Ok(Self {
+            config,
+            remote,
+            requested,
+            negotiated: None,
+            phase: ClientPhase::Connected,
+            session: None,
+        })
+    }
+
+    pub(crate) fn config(&self) -> &ClientConfig {
+        &self.config
+    }
+
+    pub(crate) fn has_hmac(&self) -> bool {
+        self.config.hmac_key.is_some()
+    }
+
+    pub(crate) fn open_packet(&self) -> Result<Vec<u8>, ClientError> {
+        match self.phase {
+            ClientPhase::Connected => {}
+            ClientPhase::Open { .. } => return Err(ClientError::AlreadyOpen),
+            ClientPhase::Closed { .. } => return Err(ClientError::AlreadyClosed),
+            ClientPhase::NoTestCompleted => return Err(ClientError::AlreadyCompleted),
+        }
+
+        let request = OpenRequest {
+            params: self.requested.clone(),
+            close: self.config.run_mode == RunMode::NoTest,
+        };
+        Ok(encode_open_request(
+            &request,
+            self.config.hmac_key.as_deref(),
+        )?)
+    }
+
+    pub(crate) fn decode_open_reply(&self, packet: &[u8]) -> Result<OpenReply, ClientError> {
+        Ok(irtt_proto::decode_open_reply(
+            packet,
+            self.config.hmac_key.as_deref(),
+        )?)
+    }
+
+    pub(crate) fn accept_open_reply<F>(
+        &mut self,
+        reply: OpenReply,
+        now: ClientTimestamp,
+        before_normal_open: F,
+    ) -> Result<OpenOutcome, ClientError>
+    where
+        F: FnOnce(&NegotiatedParams) -> Result<(), ClientError>,
+    {
+        if reply.params.protocol_version != PROTOCOL_VERSION {
+            return Err(ClientError::ProtocolVersionMismatch {
+                requested: PROTOCOL_VERSION,
+                received: reply.params.protocol_version,
+            });
+        }
+
+        let reply_is_close = flags::has(reply.flags, flags::FLAG_CLOSE);
+        match self.config.run_mode {
+            RunMode::Normal if reply_is_close => Err(ClientError::ServerRejected),
+            RunMode::Normal if reply.token == 0 => Err(ClientError::ZeroToken),
+            RunMode::Normal => self.accept_normal_open(reply, now, before_normal_open),
+            RunMode::NoTest if !reply_is_close => Err(ClientError::UnexpectedNoTestReply),
+            RunMode::NoTest if reply.token != 0 => {
+                Err(ClientError::NonZeroNoTestToken { token: reply.token })
+            }
+            RunMode::NoTest => self.accept_no_test_open(reply, now),
+        }
+    }
+
+    pub(crate) fn next_send_deadline(&self) -> Option<Instant> {
+        let session = self.session.as_ref()?;
+        if session.sending_done {
+            return None;
+        }
+        Some(session.next_send_at)
+    }
+
+    pub(crate) fn probe_timeout(&self) -> Duration {
+        self.config.probe_timeout
+    }
+
+    pub(crate) fn send_probe_with<F>(
+        &mut self,
+        override_ts: Option<ClientTimestamp>,
+        send: F,
+    ) -> Result<Vec<ClientEvent>, ClientError>
+    where
+        F: FnOnce(&[u8]) -> Result<SendProbeResult, ClientError>,
+    {
+        self.send_probe_inner(override_ts, None, send)
+    }
+
+    pub(crate) fn send_probe_for_deadline<F>(
+        &mut self,
+        scheduled_at: Instant,
+        send: F,
+    ) -> Result<Vec<ClientEvent>, ClientError>
+    where
+        F: FnOnce(&[u8]) -> Result<SendProbeResult, ClientError>,
+    {
+        self.send_probe_inner(None, Some(scheduled_at), send)
+    }
+
+    fn send_probe_inner<F>(
+        &mut self,
+        override_ts: Option<ClientTimestamp>,
+        scheduled_at_override: Option<Instant>,
+        send: F,
+    ) -> Result<Vec<ClientEvent>, ClientError>
+    where
+        F: FnOnce(&[u8]) -> Result<SendProbeResult, ClientError>,
+    {
+        let token = match self.phase {
+            ClientPhase::Open { token } => token,
+            ClientPhase::Closed { .. } => return Err(ClientError::AlreadyClosed),
+            ClientPhase::Connected => return Err(ClientError::NotOpen),
+            ClientPhase::NoTestCompleted => return Err(ClientError::AlreadyCompleted),
+        };
+
+        let session = self
+            .session
+            .as_mut()
+            .expect("session must exist when phase is Open");
+
+        if session.sending_done {
+            return Ok(vec![]);
+        }
+
+        let now = override_ts.unwrap_or_else(ClientTimestamp::now);
+
+        if let Some(end) = session.end_mono {
+            if now.mono >= end {
+                session.sending_done = true;
+                return Ok(vec![]);
+            }
+        }
+
+        session.pending.check_capacity()?;
+
+        let negotiated = self
+            .negotiated
+            .as_ref()
+            .expect("negotiated must exist when Open");
+
+        let wire_seq = session.next_wire_seq;
+        let scheduled_at = scheduled_at_override.unwrap_or(session.next_send_at);
+
+        let request = EchoRequest {
+            token,
+            sequence: wire_seq,
+            params: negotiated.params.clone(),
+            payload: vec![],
+        };
+        let packet = encode_echo_request(&request, self.config.hmac_key.as_deref())?;
+        let send_result = send(&packet)?;
+        let timer_error = instant_abs_diff(send_result.sent_at.mono, scheduled_at);
+
+        let session = self
+            .session
+            .as_mut()
+            .expect("session must exist when phase is Open");
+
+        let pending = PendingProbe {
+            wire_seq,
+            sent_at: send_result.sent_at,
+            timeout_at: send_result
+                .sent_at
+                .mono
+                .checked_add(self.config.probe_timeout)
+                .ok_or(ClientError::DurationOverflow)?,
+        };
+        session.pending.insert(pending)?;
+
+        session.next_wire_seq = session.next_wire_seq.wrapping_add(1);
+        session.packets_sent =
+            session
+                .packets_sent
+                .checked_add(1)
+                .ok_or(ClientError::CounterOverflow {
+                    counter: "packets_sent",
+                })?;
+
+        let negotiated = self
+            .negotiated
+            .as_ref()
+            .expect("negotiated must exist when Open");
+        let interval_ns = u64::try_from(negotiated.params.interval_ns)
+            .expect("validated positive negotiated interval");
+        let session = self
+            .session
+            .as_mut()
+            .expect("session must exist when phase is Open");
+        session.next_send_at = if let Some(scheduled_at) = scheduled_at_override {
+            scheduled_at
+                .checked_add(Duration::from_nanos(interval_ns))
+                .ok_or(ClientError::DurationOverflow)?
+        } else {
+            next_probe_deadline(session.start_mono, interval_ns, session.packets_sent)?
+        };
+
+        if let Some(end) = session.end_mono {
+            if session.next_send_at >= end {
+                session.sending_done = true;
+            }
+        }
+
+        Ok(vec![ClientEvent::EchoSent {
+            seq: wire_seq,
+            remote: self.remote,
+            scheduled_at,
+            sent_at: send_result.sent_at,
+            bytes: send_result.bytes,
+            send_call: send_result.send_call,
+            timer_error,
+        }])
+    }
+
+    pub(crate) fn process_received_echo_packet(
+        &mut self,
+        packet: &[u8],
+        now: ClientTimestamp,
+        meta: ReceiveMeta,
+    ) -> Result<Vec<ClientEvent>, ClientError> {
+        match self.phase {
+            ClientPhase::Open { .. } => {}
+            ClientPhase::Closed { .. } => return Err(ClientError::AlreadyClosed),
+            ClientPhase::Connected => return Err(ClientError::NotOpen),
+            ClientPhase::NoTestCompleted => return Err(ClientError::AlreadyCompleted),
+        }
+
+        let Some(reply) = self.decode_received_packet(packet) else {
+            return Ok(vec![ClientEvent::Warning {
+                kind: WarningKind::MalformedOrUnrelatedPacket,
+                message: "dropped malformed or unrelated packet".to_owned(),
+                at: now,
+            }]);
+        };
+        self.process_echo_reply(reply, packet.len(), now, meta)
+    }
+
+    pub(crate) fn poll_timeouts_at(
+        &mut self,
+        now: Instant,
+    ) -> Result<Vec<ClientEvent>, ClientError> {
+        match self.phase {
+            ClientPhase::Open { .. } => {}
+            ClientPhase::Closed { .. } => return Err(ClientError::AlreadyClosed),
+            ClientPhase::Connected => return Err(ClientError::NotOpen),
+            ClientPhase::NoTestCompleted => return Err(ClientError::AlreadyCompleted),
+        }
+
+        let session = self
+            .session
+            .as_mut()
+            .expect("session must exist when phase is Open");
+
+        let expired = session.pending.drain_expired(now);
+        let mut events = Vec::with_capacity(expired.len());
+        for probe in expired {
+            events.push(ClientEvent::EchoLoss {
+                seq: probe.wire_seq,
+                sent_at: probe.sent_at,
+                timeout_at: probe.timeout_at,
+            });
+            session.timed_out.insert(probe);
+        }
+
+        Ok(events)
+    }
+
+    pub(crate) fn close_with<F>(&mut self, send: F) -> Result<Vec<ClientEvent>, ClientError>
+    where
+        F: FnOnce(&[u8]) -> Result<(), ClientError>,
+    {
+        let token = match self.phase {
+            ClientPhase::Open { token } => token,
+            ClientPhase::Closed { .. } => return Err(ClientError::AlreadyClosed),
+            ClientPhase::Connected | ClientPhase::NoTestCompleted => {
+                return Err(ClientError::NotOpen)
+            }
+        };
+
+        let packet =
+            encode_close_request(&CloseRequest { token }, self.config.hmac_key.as_deref())?;
+        send(&packet)?;
+        self.phase = ClientPhase::Closed {
+            source: CloseSource::Local,
+        };
+        if let Some(session) = self.session.as_mut() {
+            session.timed_out.clear();
+        }
+        self.session = None;
+
+        Ok(vec![ClientEvent::SessionClosed {
+            remote: self.remote,
+            token,
+            at: ClientTimestamp::now(),
+        }])
+    }
+
+    pub(crate) fn is_run_complete(&self) -> bool {
+        let Some(session) = self.session.as_ref() else {
+            return matches!(
+                self.phase,
+                ClientPhase::Closed { .. } | ClientPhase::NoTestCompleted
+            );
+        };
+        session.sending_done && session.pending.len() == 0
+    }
+
+    pub(crate) fn is_peer_closed(&self) -> bool {
+        matches!(
+            self.phase,
+            ClientPhase::Closed {
+                source: CloseSource::Peer
+            }
+        )
+    }
+
+    pub(crate) fn has_timed_out_metadata(&self) -> bool {
+        self.session
+            .as_ref()
+            .is_some_and(|session| session.timed_out.len() > 0)
+    }
+
+    pub(crate) fn packets_sent(&self) -> u64 {
+        self.session
+            .as_ref()
+            .map_or(0, |session| session.packets_sent)
+    }
+
+    pub(crate) fn is_open(&self) -> bool {
+        matches!(self.phase, ClientPhase::Open { .. })
+    }
+
+    fn accept_normal_open<F>(
+        &mut self,
+        reply: OpenReply,
+        now: ClientTimestamp,
+        before_normal_open: F,
+    ) -> Result<OpenOutcome, ClientError>
+    where
+        F: FnOnce(&NegotiatedParams) -> Result<(), ClientError>,
+    {
+        let token = reply.token;
+        let negotiated = negotiate_params(
+            &self.requested,
+            reply.params,
+            self.config.negotiation_policy,
+        )?;
+        before_normal_open(&negotiated)?;
+        self.negotiated = Some(negotiated.clone());
+        self.phase = ClientPhase::Open { token };
+
+        let end_mono = if negotiated.params.duration_ns > 0 {
+            Some(negotiated_end_mono(
+                now.mono,
+                negotiated.params.duration_ns,
+            )?)
+        } else {
+            None
+        };
+
+        self.session = Some(ActiveSession {
+            next_wire_seq: 0,
+            highest_received_seq: None,
+            packets_sent: 0,
+            start_mono: now.mono,
+            end_mono,
+            next_send_at: now.mono,
+            pending: PendingMap::new(self.config.max_pending_probes),
+            timed_out: TimedOutMap::new(self.config.max_pending_probes),
+            completed: CompletedSet::new(self.config.max_pending_probes),
+            sending_done: false,
+        });
+
+        let event = ClientEvent::SessionStarted {
+            remote: self.remote,
+            token,
+            negotiated: negotiated.clone(),
+            at: now,
+        };
+
+        Ok(OpenOutcome::Started {
+            remote: self.remote,
+            token,
+            negotiated,
+            event,
+        })
+    }
+
+    fn accept_no_test_open(
+        &mut self,
+        reply: OpenReply,
+        now: ClientTimestamp,
+    ) -> Result<OpenOutcome, ClientError> {
+        let negotiated = negotiate_params(
+            &self.requested,
+            reply.params,
+            self.config.negotiation_policy,
+        )?;
+        self.negotiated = Some(negotiated.clone());
+        self.phase = ClientPhase::NoTestCompleted;
+        let event = ClientEvent::NoTestCompleted {
+            remote: self.remote,
+            negotiated: negotiated.clone(),
+            at: now,
+        };
+        Ok(OpenOutcome::NoTestCompleted {
+            remote: self.remote,
+            negotiated,
+            event,
+        })
+    }
+
+    fn decode_received_packet(&self, packet: &[u8]) -> Option<EchoReply> {
+        let negotiated = self
+            .negotiated
+            .as_ref()
+            .expect("negotiated must exist when Open");
+
+        decode_echo_reply(packet, &negotiated.params, self.config.hmac_key.as_deref()).ok()
+    }
+
+    fn process_echo_reply(
+        &mut self,
+        reply: EchoReply,
+        packet_len: usize,
+        now: ClientTimestamp,
+        meta: ReceiveMeta,
+    ) -> Result<Vec<ClientEvent>, ClientError> {
+        let token = match self.phase {
+            ClientPhase::Open { token } => token,
+            _ => unreachable!(),
+        };
+        if reply.token != token {
+            return Ok(vec![ClientEvent::Warning {
+                kind: WarningKind::WrongToken,
+                message: format!(
+                    "dropped reply with wrong token: expected {token:#x}, got {:#x}",
+                    reply.token
+                ),
+                at: now,
+            }]);
+        }
+
+        let session = self.session.as_mut().expect("session must exist when Open");
+
+        let wire_seq = reply.sequence;
+
+        if let Some(pending) = session.pending.remove(wire_seq) {
+            let rtt = compute_rtt(&pending.sent_at, &now, &reply.timestamps);
+            let server_timing = build_server_timing(&reply.timestamps);
+            let one_way = compute_one_way(&pending.sent_at, &now, &reply.timestamps);
+            let received_stats = build_received_stats(&reply);
+            let is_late = session
+                .highest_received_seq
+                .is_some_and(|h| sequence_is_before(wire_seq, h));
+            let highest_seen = session.highest_received_seq.unwrap_or(wire_seq);
+
+            update_highest_received(&mut session.highest_received_seq, wire_seq);
+            session.completed.insert(wire_seq);
+
+            let mut events = Vec::new();
+            if is_late {
+                events.push(ClientEvent::LateReply {
+                    seq: wire_seq,
+                    highest_seen,
+                    remote: self.remote,
+                    sent_at: Some(pending.sent_at),
+                    received_at: now,
+                    rtt: Some(rtt),
+                    server_timing,
+                    one_way,
+                    received_stats,
+                    bytes: packet_len,
+                    packet_meta: meta.into(),
+                });
+            } else {
+                events.push(ClientEvent::EchoReply {
+                    seq: wire_seq,
+                    remote: self.remote,
+                    sent_at: pending.sent_at,
+                    received_at: now,
+                    rtt,
+                    server_timing,
+                    one_way,
+                    received_stats,
+                    bytes: packet_len,
+                    packet_meta: meta.into(),
+                });
+            }
+            if flags::has(reply.flags, flags::FLAG_CLOSE) {
+                self.close_from_peer(token, now, &mut events);
+            }
+            Ok(events)
+        } else if session.completed.contains(wire_seq) {
+            update_highest_received(&mut session.highest_received_seq, wire_seq);
+            Ok(vec![ClientEvent::DuplicateReply {
+                seq: wire_seq,
+                remote: self.remote,
+                received_at: now,
+                bytes: packet_len,
+            }])
+        } else if let Some(timed_out) = session.timed_out.remove(wire_seq) {
+            let rtt = compute_rtt(&timed_out.sent_at, &now, &reply.timestamps);
+            let server_timing = build_server_timing(&reply.timestamps);
+            let one_way = compute_one_way(&timed_out.sent_at, &now, &reply.timestamps);
+            let received_stats = build_received_stats(&reply);
+            let highest_seen = session.highest_received_seq.unwrap_or(wire_seq);
+            update_highest_received(&mut session.highest_received_seq, wire_seq);
+            session.completed.insert(wire_seq);
+
+            let mut events = vec![ClientEvent::LateReply {
+                seq: wire_seq,
+                highest_seen,
+                remote: self.remote,
+                sent_at: Some(timed_out.sent_at),
+                received_at: now,
+                rtt: Some(rtt),
+                server_timing,
+                one_way,
+                received_stats,
+                bytes: packet_len,
+                packet_meta: meta.into(),
+            }];
+            if flags::has(reply.flags, flags::FLAG_CLOSE) {
+                self.close_from_peer(token, now, &mut events);
+            }
+            Ok(events)
+        } else if session
+            .highest_received_seq
+            .is_some_and(|h| sequence_is_before(wire_seq, h))
+        {
+            Ok(vec![ClientEvent::LateReply {
+                seq: wire_seq,
+                highest_seen: session.highest_received_seq.unwrap(),
+                remote: self.remote,
+                sent_at: None,
+                received_at: now,
+                rtt: None,
+                server_timing: build_server_timing(&reply.timestamps),
+                one_way: None,
+                received_stats: build_received_stats(&reply),
+                bytes: packet_len,
+                packet_meta: meta.into(),
+            }])
+        } else {
+            Ok(vec![ClientEvent::Warning {
+                kind: WarningKind::UntrackedReply,
+                message: format!(
+                    "dropped reply with untracked seq {wire_seq} (no pending or completed entry)"
+                ),
+                at: now,
+            }])
+        }
+    }
+
+    fn close_from_peer(&mut self, token: u64, now: ClientTimestamp, events: &mut Vec<ClientEvent>) {
+        self.phase = ClientPhase::Closed {
+            source: CloseSource::Peer,
+        };
+        if let Some(session) = self.session.as_mut() {
+            session.timed_out.clear();
+        }
+        self.session = None;
+        events.push(ClientEvent::SessionClosed {
+            remote: self.remote,
+            token,
+            at: now,
+        });
+    }
+}
+
+pub(crate) fn recv_buffer_size(
+    has_hmac: bool,
+    negotiated: Option<&NegotiatedParams>,
+) -> Result<usize, ClientError> {
+    Ok(match negotiated {
+        Some(negotiated) => echo_packet_len(has_hmac, &negotiated.params)?
+            .saturating_add(1)
+            .max(MIN_RECV_BUFFER_SIZE),
+        None => MIN_RECV_BUFFER_SIZE,
+    })
+}
+
+pub(crate) fn params_from_config(config: &ClientConfig) -> Result<Params, ClientError> {
+    validate_protocol_config(config)?;
+    Ok(Params {
+        protocol_version: PROTOCOL_VERSION,
+        duration_ns: match config.duration {
+            Some(duration) => config_duration_to_ns("duration", duration)?,
+            None => 0,
+        },
+        interval_ns: config_duration_to_ns("interval", config.interval)?,
+        length: i64::from(config.length),
+        received_stats: config.received_stats,
+        stamp_at: config.stamp_at,
+        clock: config.clock,
+        dscp: i64::from(config.dscp),
+        server_fill: config.server_fill.clone().map(|value| ServerFill { value }),
+    })
+}
+
+pub(crate) fn update_highest_received(highest_received_seq: &mut Option<u32>, wire_seq: u32) {
+    *highest_received_seq = Some(highest_received_seq.map_or(wire_seq, |h| {
+        if sequence_is_after(wire_seq, h) {
+            wire_seq
+        } else {
+            h
+        }
+    }));
+}
+
+fn next_probe_deadline(
+    start: Instant,
+    interval_ns: u64,
+    packets_sent: u64,
+) -> Result<Instant, ClientError> {
+    let offset_ns = interval_ns
+        .checked_mul(packets_sent)
+        .ok_or(ClientError::DurationOverflow)?;
+    start
+        .checked_add(Duration::from_nanos(offset_ns))
+        .ok_or(ClientError::DurationOverflow)
+}
+
+pub(crate) fn sequence_is_after(candidate: u32, current: u32) -> bool {
+    candidate != current && candidate.wrapping_sub(current) < (1 << 31)
+}
+
+pub(crate) fn sequence_is_before(candidate: u32, current: u32) -> bool {
+    current != candidate && current.wrapping_sub(candidate) < (1 << 31)
+}
+
+fn instant_abs_diff(left: Instant, right: Instant) -> Duration {
+    left.checked_duration_since(right)
+        .or_else(|| right.checked_duration_since(left))
+        .unwrap_or(Duration::ZERO)
+}
+
+pub(crate) fn compute_rtt(
+    sent_at: &ClientTimestamp,
+    received_at: &ClientTimestamp,
+    ts: &TimestampFields,
+) -> RttSample {
+    let raw = received_at
+        .mono
+        .checked_duration_since(sent_at.mono)
+        .unwrap_or(Duration::ZERO);
+
+    let server_processing = compute_server_processing(ts);
+
+    let adjusted = server_processing
+        .map(|sp| SignedDuration::from_nanos(duration_ns_i128(raw) - duration_ns_i128(sp)));
+    let effective = adjusted.unwrap_or_else(|| SignedDuration::from_duration(raw));
+
+    RttSample {
+        raw,
+        adjusted,
+        effective,
+    }
+}
+
+fn duration_ns_i128(duration: Duration) -> i128 {
+    i128::try_from(duration.as_nanos()).unwrap_or(i128::MAX)
+}
+
+fn compute_server_processing(ts: &TimestampFields) -> Option<Duration> {
+    if let (Some(recv_mono), Some(send_mono)) = (ts.recv_mono, ts.send_mono) {
+        let diff = send_mono.checked_sub(recv_mono)?;
+        return Some(Duration::from_nanos(u64::try_from(diff).ok()?));
+    }
+    if let (Some(recv_wall), Some(send_wall)) = (ts.recv_wall, ts.send_wall) {
+        let diff = send_wall.checked_sub(recv_wall)?;
+        return Some(Duration::from_nanos(u64::try_from(diff).ok()?));
+    }
+    None
+}
+
+fn build_server_timing(ts: &TimestampFields) -> Option<ServerTiming> {
+    if ts.recv_wall.is_none()
+        && ts.recv_mono.is_none()
+        && ts.send_wall.is_none()
+        && ts.send_mono.is_none()
+        && ts.midpoint_wall.is_none()
+        && ts.midpoint_mono.is_none()
+    {
+        return None;
+    }
+    Some(ServerTiming {
+        receive_wall_ns: ts.recv_wall,
+        receive_mono_ns: ts.recv_mono,
+        send_wall_ns: ts.send_wall,
+        send_mono_ns: ts.send_mono,
+        midpoint_wall_ns: ts.midpoint_wall,
+        midpoint_mono_ns: ts.midpoint_mono,
+        processing: compute_server_processing(ts),
+    })
+}
+
+pub(crate) fn compute_one_way(
+    sent_at: &ClientTimestamp,
+    received_at: &ClientTimestamp,
+    ts: &TimestampFields,
+) -> Option<OneWayDelaySample> {
+    let server_recv_wall = ts.recv_wall.or(ts.midpoint_wall);
+    let server_send_wall = ts.send_wall.or(ts.midpoint_wall);
+
+    let client_send_ns = unix_epoch_ns_i64(sent_at.wall);
+    let client_recv_ns = unix_epoch_ns_i64(received_at.wall);
+
+    let c2s = server_recv_wall
+        .zip(client_send_ns)
+        .and_then(|(srv, cli)| srv.checked_sub(cli))
+        .map(|d| SignedDuration::from_nanos(i128::from(d)));
+    let s2c = client_recv_ns
+        .zip(server_send_wall)
+        .and_then(|(cli, srv)| cli.checked_sub(srv))
+        .map(|d| SignedDuration::from_nanos(i128::from(d)));
+
+    if c2s.is_none() && s2c.is_none() {
+        return None;
+    }
+
+    Some(OneWayDelaySample {
+        client_to_server: c2s,
+        server_to_client: s2c,
+    })
+}
+
+pub(crate) fn unix_epoch_ns_i64(time: SystemTime) -> Option<i64> {
+    time.duration_since(UNIX_EPOCH)
+        .ok()
+        .and_then(|duration| i64::try_from(duration.as_nanos()).ok())
+}
+
+fn build_received_stats(reply: &EchoReply) -> Option<ReceivedStatsSample> {
+    if reply.recv_count.is_none() && reply.recv_window.is_none() {
+        return None;
+    }
+    Some(ReceivedStatsSample {
+        count: reply.recv_count,
+        window: reply.recv_window,
+    })
+}
+
+fn validate_protocol_config(config: &ClientConfig) -> Result<(), ClientError> {
+    if config.duration == Some(Duration::ZERO) {
+        return Err(ClientError::InvalidConfig {
+            reason: "duration must be greater than zero; use None for continuous mode".to_owned(),
+        });
+    }
+    if config.interval == Duration::ZERO {
+        return Err(ClientError::InvalidConfig {
+            reason: "interval must be greater than zero".to_owned(),
+        });
+    }
+    if config.dscp > MAX_DSCP_CODEPOINT {
+        return Err(ClientError::InvalidConfig {
+            reason: format!("dscp must be <= {MAX_DSCP_CODEPOINT}"),
+        });
+    }
+    if config.length > MAX_UDP_PAYLOAD_LENGTH {
+        return Err(ClientError::InvalidConfig {
+            reason: format!("packet length must be <= {MAX_UDP_PAYLOAD_LENGTH}"),
+        });
+    }
+
+    if let Some(fill) = &config.server_fill {
+        let len = fill.len();
+        if len == 0 {
+            return Err(ClientError::InvalidConfig {
+                reason: "server_fill must not be empty".to_owned(),
+            });
+        }
+        if len > MAX_SERVER_FILL_BYTES {
+            return Err(ClientError::InvalidConfig {
+                reason: format!("server_fill must be <= {MAX_SERVER_FILL_BYTES} bytes, got {len}"),
+            });
+        }
+    }
+
+    Ok(())
+}
+
+fn config_duration_to_ns(field: &str, duration: Duration) -> Result<i64, ClientError> {
+    i64::try_from(duration.as_nanos()).map_err(|_| ClientError::InvalidConfig {
+        reason: format!("{field} is too large to encode as nanoseconds"),
+    })
+}
+
+fn negotiated_end_mono(start: Instant, duration_ns: i64) -> Result<Instant, ClientError> {
+    debug_assert!(duration_ns > 0);
+    let duration_ns = u64::try_from(duration_ns).expect("validated positive negotiated duration");
+    start
+        .checked_add(Duration::from_nanos(duration_ns))
+        .ok_or_else(|| ClientError::NegotiationRejected {
+            reason: "duration is too large to schedule".to_owned(),
+        })
+}

crates/irtt-client/src/session.rs

@@ -161,7 +161,13 @@ pub(crate) enum ClientPhase {
     Connected,
     Open { token: u64 },
     NoTestCompleted,
-    Closed,
+    Closed { source: CloseSource },
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum CloseSource {
+    Local,
+    Peer,
 }
 
 #[derive(Debug)]

crates/irtt-client/src/socket.rs

@@ -99,6 +99,44 @@ pub(crate) fn connect_udp_socket(
     Ok(socket)
 }
 
+pub(crate) fn bind_unconnected_udp_socket(
+    config: &SocketConfig,
+    family_remote: SocketAddr,
+) -> Result<UdpSocket, ClientError> {
+    let domain = if family_remote.is_ipv4() {
+        Domain::IPV4
+    } else {
+        Domain::IPV6
+    };
+    let socket = Socket::new(domain, Type::DGRAM, Some(Protocol::UDP))?;
+
+    if config.ipv6_only && family_remote.is_ipv6() {
+        socket.set_only_v6(true)?;
+    }
+    let bind_addr = config.bind_addr.unwrap_or_else(|| {
+        if family_remote.is_ipv4() {
+            SocketAddr::from(([0, 0, 0, 0], 0))
+        } else {
+            SocketAddr::from(([0_u16; 8], 0))
+        }
+    });
+    socket.bind(&bind_addr.into())?;
+
+    let socket: UdpSocket = socket.into();
+    configure_receive_metadata(&socket, family_remote).map_err(|source| {
+        ClientError::SocketOption {
+            operation: "enable receive metadata",
+            remote: family_remote,
+            source,
+        }
+    })?;
+    if let Some(ttl) = config.ttl {
+        apply_ttl_to_socket(&socket, family_remote, ttl)?;
+    }
+    socket.set_read_timeout(config.recv_timeout)?;
+    Ok(socket)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/irtt-proto/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-proto"
-version = "0.3.0"
+version = "0.4.0"
 description = "IRTT protocol encoding and decoding primitives"
 edition.workspace = true
 license.workspace = true

crates/irtt-stats/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-stats"
-version = "0.3.0"
+version = "0.4.0"
 description = "Statistics aggregation for irtt-client events"
 edition.workspace = true
 license.workspace = true

deny.toml

@@ -44,6 +44,7 @@ allow = [
     "Apache-2.0",
     "Unicode-3.0",
     "BSD-3-Clause",
+    "Zlib"
 ]
 
 exceptions = [

dist-workspace.toml

@@ -11,4 +11,5 @@ ci = "github"
 installers = []
 # Target platforms to build apps for (Rust target-triple syntax)
 targets = ["aarch64-apple-darwin", "aarch64-unknown-linux-gnu", "x86_64-apple-darwin", "x86_64-unknown-linux-gnu", "x86_64-unknown-linux-musl", "x86_64-pc-windows-msvc"]
-features = ["tui"]
+# Features to pass to cargo build
+features = ["full"]

scripts/compare_irtt_clients.py

@@ -9,6 +9,7 @@ the local Rust client output.
 from __future__ import annotations
 
 import argparse
+import csv
 import datetime as dt
 import json
 import math
@@ -147,7 +148,7 @@ def parse_args() -> argparse.Namespace:
         default=DEFAULT_IRTT_RS_COMMAND,
         help=(
             "Command prefix or direct path for the Rust client. Arguments for "
-            "target, duration, interval, and machine output are appended. "
+            "target, duration, interval, and CSV event output are appended. "
             f"Default: {DEFAULT_IRTT_RS_COMMAND!r}"
         ),
     )
@@ -386,8 +387,10 @@ def run_case(
         case.duration,
         "--interval",
         case.interval,
-        "--output",
-        "machine",
+        "--format",
+        "csv",
+        "--columns",
+        "event,seq,effective_rtt_us,raw_rtt_us,adjusted_rtt_us,server_processing_us,client_send_wall_ns",
         *args.rust_extra_arg,
     ]
 
@@ -402,7 +405,7 @@ def run_case(
 
     rust_samples = case_dir / "irtt-rs-rtt-samples.csv"
     upstream_samples = case_dir / "upstream-rtt-samples.csv"
-    rust_metrics = parse_rust_machine(case_dir / "irtt-rs.stdout", rust_samples)
+    rust_metrics = parse_rust_csv(case_dir / "irtt-rs.stdout", rust_samples)
     upstream_metrics = parse_upstream(case_dir / "upstream.stdout", upstream_json, upstream_samples)
 
     comparison = classify_difference(upstream_metrics, rust_metrics)
@@ -529,16 +532,7 @@ def wait_process(proc: subprocess.Popen[bytes] | None) -> int:
             return proc.wait()
 
 
-def parse_kv_line(line: str) -> dict[str, str]:
-    fields: dict[str, str] = {}
-    for token in shlex.split(line):
-        if "=" in token:
-            key, value = token.split("=", 1)
-            fields[key] = value
-    return fields
-
-
-def parse_rust_machine(path: Path, samples_path: Path) -> Metrics:
+def parse_rust_csv(path: Path, samples_path: Path) -> Metrics:
     metrics = Metrics(source="irtt-rs", samples_path=str(samples_path))
     effective: list[float] = []
     raw: list[float] = []
@@ -552,11 +546,11 @@ def parse_rust_machine(path: Path, samples_path: Path) -> Metrics:
         metrics.parse_notes.append(f"missing {path}")
         return metrics
 
-    for line in path.read_text(encoding="utf-8", errors="replace").splitlines():
-        if not line.strip():
-            continue
-        fields = parse_kv_line(line)
+    text = path.read_text(encoding="utf-8", errors="replace")
+    for fields in csv.DictReader(line for line in text.splitlines() if line.strip()):
         event = fields.get("event")
+        if event is None:
+            continue
         seq = parse_int(fields.get("seq"))
         if event == "echo_reply":
             if seq is not None: