irtt-rs

irtt-rs is a Rust implementation of an IRTT-compatible client and server: finite or continuous UDP latency probing, plus the server side those probes run against.

This is not the upstream IRTT project. For the original implementation, protocol background, and broader documentation, see heistp/irtt. The installed dispatcher is named irtt-rs rather than irtt to avoid conflicting with or being mistaken for it.

Features

• Finite and continuous probe sessions
• Concurrent probing of multiple targets, with staggered or burst pacing
• Reusable client library with a structured event stream (blocking, Tokio, or managed)
• Human-readable table output, plus CSV, TSV, and JSON Lines for scripts and monitoring systems, with selectable output columns
• Optional terminal UI
• Reusable Tokio-native server library
• UDP server applet with sensible zero-argument defaults and explicit bind and session-policy options
• Router-friendly multi-applet binary layout

Comparison with upstream IRTT

irtt-rs is an independent, compatible reimplementation, not a successor or replacement for upstream IRTT — heistp/irtt remains the original implementation. Interoperability is a project goal; see docs/INTEROP_COMPARISON.md and docs/protocol/ for the black-box interoperability methodology and protocol baseline this project verifies against. Choose between them based on the capabilities and deployment model you need.

The table below was checked against upstream release v0.9.2 (2026-07-17). This project's own interop testing and protocol baseline are currently pinned to the prior release, v0.9.1; the wire protocol version number is unchanged between the two, but v0.9.2 has not itself been exercised against this project's interop harness.

Capability	irtt-rs	upstream IRTT (v0.9.2)
Wire protocol	Protocol version 1, verified against upstream v0.9.1	Protocol version 1 (unchanged in v0.9.2)
Finite probing	Supported, default 10s	Supported, default 1m
Continuous/indefinite operation	Supported (--duration 0); still computes running statistics (see below)	Supported via streaming mode (-s, added in v0.9.2); computes no statistics at all in that mode
Statistics in continuous mode	Running count/min/max/mean/variance per target; exact medians unavailable; bounded IPDV tracking	None in streaming mode — raw/event output only, by design, to avoid unbounded memory
Multi-target probing (one invocation)	Supported, with labels and staggered/burst pacing	Not supported — one remote address per invocation
Terminal UI	irtt-tui, a live graph/dashboard applet	Not present
Output formats	table, csv, tsv, jsonl, with selectable columns	Text summary, JSON (optionally gzip to file), and a fixed-field raw mode; no CSV/TSV and no column selection
Client/server library API	Separate, independently versioned Rust crates (irtt-client, irtt-server)	One combined Go package exposing both roles
Server: multiple listeners	ServerSet supervises several listeners in one process	ListenAndServe also serves multiple requested addresses
Server: wildcard reply-source	Default behavior on Linux/macOS/FreeBSD; refused elsewhere rather than served incorrectly	Opt-in via --set-src-ip, with a documented per-packet allocation cost
Server: zero-argument bind	Binds the wildcard address on both families by default, gated by the platform check above	Binds the wildcard address on both families by default; no documented platform gate
Prebuilt release binaries	Published for six target triples	None published; install via go install or manual build

Upstream has capabilities this project does not implement: a report subcommand for replaying saved JSON results, benchmarking and timer/clock-diagnostic subcommands, client-side payload fill and don't-fragment/wait-strategy/timer-algorithm controls, an operator-configurable server-side fill policy (this project's server always honors a session's negotiated fill request, with a fixed fallback pattern, but has no equivalent to upstream's flags for restricting or overriding it), syslog logging, and bundled systemd/OpenRC service files.

This project has capabilities upstream does not implement: multi-target probing with labels, the terminal UI, CSV/TSV output with selectable columns, a quantified and actively-warned memory-retention model for long-running client sessions, and best-effort Linux kernel-timestamp preference for its own send/receive endpoint.

Installation

The build requires Rust 1.88 or newer.

Install the latest release from crates.io:

cargo install irtt-rs --locked

This installs the irtt-rs dispatcher plus dedicated irtt-client, irtt-tui, and irtt-server binaries. Each applet can also be built in isolation with --no-default-features plus the applet's own feature, for example a lightweight client-only install:

cargo install irtt-rs --locked --no-default-features --features client

For development, or to install directly from a checkout:

git clone https://github.com/Lochnair/irtt-rs.git
cd irtt-rs
cargo install --path crates/irtt-app --locked

Quick start

Probe a server:

irtt-client netperf-eu.bufferbloat.net:2112 --duration 30s --interval 100ms

Probe continuously until interrupted (Ctrl-C):

irtt-client netperf-eu.bufferbloat.net:2112 --duration 0

Watch the same session live in the terminal UI:

irtt-tui netperf-eu.bufferbloat.net:2112

Run a server with sensible defaults — no --bind needed:

irtt-server

Documentation

• docs/irtt-client.md — target syntax, output formats and columns, measurement field definitions, finite/continuous memory behavior, kernel timestamps.
• docs/irtt-tui.md — controls, continuous default, retained history.
• docs/irtt-server.md — bind defaults and overrides, wildcard listener behavior, session policy, HMAC.
• docs/irtt-rs.md — the multicall dispatcher, applet binary names, feature-gated builds.
• docs.rs for the library crates below.
• docs/protocol/ and docs/INTEROP_COMPARISON.md for the wire protocol specification and interoperability validation against upstream irtt.

Every applet also documents its full option list with --help.

Crates

Crate	crates.io	What it is
irtt-rs	crates.io	Application package: the irtt-rs, irtt-client, irtt-tui, and irtt-server binaries
irtt-client	crates.io	Reusable client/session library (docs.rs)
irtt-server	crates.io	Reusable Tokio-native server library (docs.rs)
irtt-stats	crates.io	Statistics aggregation over irtt-client events (docs.rs)
irtt-proto	crates.io	Low-level wire protocol encode/decode (docs.rs)

Each library crate has its own crates.io README describing what it's for and when to use it instead of irtt-client/irtt-server directly.

Binaries and features

Build	Binaries
--no-default-features	irtt-rs
--no-default-features --features client	irtt-rs, irtt-client
--no-default-features --features server	irtt-rs, irtt-server
--no-default-features --features tui	irtt-rs, irtt-tui
Default features (or --all-features)	irtt-rs, irtt-client, irtt-tui, irtt-server

Development

cargo fmt --all -- --check
cargo test --workspace --locked
cargo clippy --workspace --all-targets --all-features --locked -- -D warnings

See AGENTS.md for architecture, testing policy, and the clean-room provenance boundary this project maintains against upstream irtt.