tcp-proxy

A small, async TCP port‑forwarding proxy built with Rust and Tokio. It listens on a local address/port and forwards raw bytes bidirectionally to a target address/port. Includes structured logging via tracing.

Quick Start

# Build
cargo build --release

# Run (info logs by default)
RUST_LOG=info ./target/release/tcp-proxy \
  --listen 127.0.0.1:5000 \
  --to 127.0.0.1:6000

Usage

tcp-proxy --listen <ADDR:PORT> --to <ADDR:PORT> \
          [--connect-timeout <DURATION>]

• --listen <ADDR:PORT>: Local address:port to accept client connections (e.g., 0.0.0.0:5000).
• --to <ADDR:PORT>: Remote target address:port to forward to (e.g., 10.1.1.10:6000).
• --connect-timeout <DURATION>: Max time to establish the outbound connection (default: 5s).

Durations use humantime format, e.g., 250ms, 10s, 2m, 1h.

Examples

• Forward local port 5000 to 10.1.1.10:6000:

  RUST_LOG=info tcp-proxy --listen 0.0.0.0:5000 --to 10.1.1.10:6000

• With a 2s connect timeout:

  tcp-proxy --listen 127.0.0.1:5000 --to 127.0.0.1:6000 \
    --connect-timeout 2s

• Quick local test with netcat:

  # Terminal A: echo server on 6000
  nc -lk 127.0.0.1 6000
  
  # Terminal B: run proxy 5001 -> 6000
  tcp-proxy --listen 127.0.0.1:5001 --to 127.0.0.1:6000
  
  # Terminal C: connect to proxy and type
  nc 127.0.0.1 5001

Logging

• Uses tracing with environment-based filtering. Default level is info.
• Control verbosity with RUST_LOG:
  • RUST_LOG=warn tcp-proxy ... (only warnings and errors)
  • RUST_LOG=info tcp-proxy ... (normal output; default)
  • RUST_LOG=tcp_proxy=debug tcp-proxy ... (enable debug for this crate only)
• Connection context: logs emitted while handling a connection are prefixed with a span like conn{id=..., client=..., remote=...}.

Notes

• On Ctrl+C, the proxy exits immediately; active connections are aborted.
• On connect timeout, the client socket is closed and the attempt is logged as a warning.
• No authentication, authorization, or TLS.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT License (LICENSE-MIT)

at your option.