xfr

A modern iperf3 alternative with a live TUI, multi-client server, MPTCP, and QUIC support. Built in Rust.

Quick Start

# Server
xfr serve

# Client (in another terminal or machine)
xfr 192.168.1.1              # Basic TCP test
xfr 192.168.1.1 -b 100M      # TCP at 100 Mbps
xfr 192.168.1.1 -P 4         # 4 parallel streams
xfr 192.168.1.1 -u -b 1G     # UDP at 1 Gbps

See Installation below for setup instructions.

TUI Preview

Features

Live TUI with real-time throughput graphs and per-stream stats
Server dashboard - xfr serve --tui for monitoring active tests
Multi-client server - handle multiple simultaneous tests
TCP, UDP, QUIC, and MPTCP with configurable bitrate pacing and parallel streams
Firewall-friendly - single-port TCP, QUIC multiplexing, and --cport for pinning UDP/QUIC/TCP data source ports
Bidirectional testing - measure upload and download simultaneously
Multiple output formats - plain text, JSON, JSON streaming, CSV
Result comparison - xfr diff to detect performance regressions
LAN discovery - find xfr servers with mDNS (xfr discover)
Prometheus metrics - export stats for monitoring dashboards
Config file - save defaults in ~/.config/xfr/config.toml
Environment variables - XFR_PORT, XFR_DURATION overrides

vs iperf3

| Feature | iperf3 | xfr | |---------|--------|-----| | Live TUI | No | Yes (client & server) | | Multi-client server | No | Yes | | MPTCP | No | Yes (auto on server, --mptcp on client, Linux 5.6+) | | Firewall-friendly | --cport (TCP/UDP) | Single-port TCP + --cport (UDP/QUIC/TCP data) | | Output formats | Text/JSON | Text/JSON/CSV | | Prometheus metrics | No | Yes (optional feature) | | Compare runs | No | xfr diff | | LAN discovery | No | xfr discover | | Config file | No | Yes |

Real-World Use Cases

VPN Tunnel Testing

Measure actual throughput through your VPN:

# On VPN server
xfr serve

# From client, through VPN
xfr 10.8.0.1 -t 30s

UDP Congestion Detection

Test UDP at your expected rate to detect packet loss:

xfr <host> -u -b 500M -t 60s    # Watch for loss percentage in TUI

Before/After Comparison

Quantify the impact of network changes:

xfr <host> --json -o before.json
# ... make changes ...
xfr <host> --json -o after.json
xfr diff before.json after.json --threshold 5

Multi-Stream for Bonded Connections

Test aggregate bandwidth across bonded/LACP interfaces:

xfr <host> -P 8 -t 30s          # 8 streams to utilize all links

Prometheus Monitoring

Continuous performance monitoring:

xfr serve --prometheus 9090 --push-gateway http://pushgateway:9091
# Scrape metrics or view in Grafana

Installation

From crates.io (Recommended)

Requires Rust 1.88+:

# Install Rust (if not already installed)
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source ~/.cargo/env

# Install xfr
cargo install xfr

Homebrew (macOS/Linux)

brew install lance0/tap/xfr

Pre-built Binaries

Download from GitHub Releases:

| Platform | Target | |----------|--------| | Linux x86_64 | xfr-x86_64-unknown-linux-musl.tar.gz | | Linux ARM64 | xfr-aarch64-unknown-linux-gnu.tar.gz | | macOS Apple Silicon | xfr-aarch64-apple-darwin.tar.gz | | macOS Intel | Use cargo install xfr | | Android (Termux) | xfr-aarch64-linux-android.tar.gz | | Windows | Use WSL2 (native support is experimental) |

# Example: Linux x86_64
curl -LO https://github.com/lance0/xfr/releases/latest/download/xfr-x86_64-unknown-linux-musl.tar.gz
tar xzf xfr-*.tar.gz && sudo mv xfr /usr/local/bin/

eget

eget lance0/xfr

Arch Linux (AUR)

yay -S xfr-bin

From Source

git clone https://github.com/lance0/xfr
cd xfr && cargo build --release
sudo cp target/release/xfr /usr/local/bin/

Quick Install Script

Note: Review scripts before piping to sh. See the install script source.

curl -fsSL https://raw.githubusercontent.com/lance0/xfr/master/install.sh | sh

Termux (Android)

Download the aarch64-linux-android binary from releases, or build from source:

pkg install rust
cargo install xfr

Nix

nix run github:lance0/xfr          # Run without installing
nix profile install github:lance0/xfr  # Install to profile

Or add to your flake inputs:

inputs.xfr.url = "github:lance0/xfr";

A dev shell is also available via nix develop.

NetBSD

Available via pkgsrc:

pkgin install xfr

Optional Features

| Feature | Default | Description | |---------|---------|-------------| | discovery | Yes | mDNS LAN discovery (xfr discover) | | prometheus | No | Prometheus metrics endpoint and Push Gateway support |

cargo install xfr --features prometheus    # Prometheus support
cargo install xfr --all-features           # All features

Shell Completions

# Bash
xfr --completions bash > ~/.local/share/bash-completion/completions/xfr

# Zsh (add ~/.zfunc to fpath in .zshrc first)
xfr --completions zsh > ~/.zfunc/_xfr

# Fish
xfr --completions fish > ~/.config/fish/completions/xfr.fish

# PowerShell (add to $PROFILE)
xfr --completions powershell >> $PROFILE

# Elvish
xfr --completions elvish > ~/.elvish/lib/xfr.elv

Usage

Server

xfr serve                    # Listen on port 5201
xfr serve -p 9000            # Custom port
xfr serve --tui              # Live dashboard showing active tests
xfr serve --one-off          # Exit after one test
xfr serve --max-duration 60s # Limit test duration
xfr serve --push-gateway http://pushgateway:9091  # Push metrics on test complete
xfr serve --psk mysecret     # Require PSK authentication
xfr serve --rate-limit 2     # Max 2 concurrent tests per IP
xfr serve --allow 192.168.0.0/16 --deny 0.0.0.0/0  # IP ACL

Client

xfr 192.168.1.1              # TCP test, 10s, single stream
xfr 192.168.1.1 -t 30s       # 30 second test
xfr 192.168.1.1 -P 4         # 4 parallel streams
xfr 192.168.1.1 -R           # Reverse (download test)
xfr 192.168.1.1 --bidir      # Bidirectional
xfr 192.168.1.1 -6           # Force IPv6 only
xfr ::1 -6                   # IPv6 localhost

UDP Mode

xfr 192.168.1.1 -u           # UDP mode
xfr 192.168.1.1 -u -b 1G     # UDP at 1 Gbps
xfr 192.168.1.1 -u -b 100M   # UDP at 100 Mbps

QUIC Mode

xfr 192.168.1.1 --quic       # QUIC transport (encrypted)
xfr 192.168.1.1 --quic -P 4  # QUIC with 4 parallel streams
xfr 192.168.1.1 --quic -R    # QUIC download test

QUIC provides built-in TLS 1.3 encryption with stream multiplexing over a single connection.

Security Note: QUIC encrypts traffic but does not verify server identity by default. For authenticated connections, use --psk on both client and server to prevent MITM attacks.

MPTCP Mode

xfr 192.168.1.1 --mptcp       # MPTCP (Multi-Path TCP, Linux 5.6+)
xfr 192.168.1.1 --mptcp -P 4  # MPTCP with 4 parallel streams
xfr 192.168.1.1 --mptcp -R    # MPTCP download test

MPTCP enables a single connection to use multiple network paths simultaneously (e.g., WiFi + Ethernet). The server automatically creates MPTCP listeners — no flag needed on the server side. All TCP features (nodelay, congestion control, window size, bidir, multi-stream) work transparently with MPTCP.

Output Formats

xfr <host> --json              # JSON summary
xfr <host> --json-stream       # JSON per interval (for scripting)
xfr <host> --csv               # CSV output
xfr <host> -q                  # Quiet mode (summary only)
xfr <host> -o results.json     # Save to file
xfr <host> --no-tui            # Plain text, no TUI
xfr <host> --timestamp-format iso8601  # ISO 8601 timestamps

Note: Log messages go to stderr, allowing clean JSON/CSV piping: xfr <host> --json 2>/dev/null

Interval Control

xfr <host> -i 2                # Report every 2 seconds
xfr <host> --omit 3            # Skip first 3s of intervals (TCP ramp-up)

Compare Results

xfr diff baseline.json current.json
xfr diff baseline.json current.json --threshold 5

Discovery

xfr discover                 # Find xfr servers on LAN
xfr discover --timeout 10s   # Extended search

Keybindings (Client TUI)

| Key | Action | |-----|--------| | q | Quit (cancels test) | | p | Pause/Resume display | | s | Settings modal | | t | Cycle color theme | | d | Toggle per-stream view | | ? / F1 | Help | | j | Print JSON result | | u | Dismiss update notification |

Keybindings (Server TUI)

| Key | Action | |-----|--------| | q | Quit server | | ? / F1 | Help | | Esc | Close help |

Themes

xfr includes 11 built-in color themes. Select with --theme or press t during a test:

xfr <host> --theme dracula     # Dark purple theme
xfr <host> --theme matrix      # Green on black hacker style
xfr <host> --theme catppuccin  # Soothing pastels
xfr <host> --theme nord        # Arctic blue tones

Available themes: default, kawaii, cyber, dracula, monochrome, `matr

Xfr

Install / Use

README

xfr