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Tag 0.1.7
Critical bug fixes

Signed-off-by: Jacob Kiers <code@kiers.eu>
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Hey, now we are on level 4!


Under heavy development, version 0.1 may update frequently

Fourth is a layer 4 proxy implemented by Rust to listen on specific ports and transfer TCP/KCP data to remote addresses(only TCP) according to configuration.


  • Listen on specific port and proxy to local or remote port
  • SNI-based rule without terminating TLS connection
  • Allow KCP inbound(warning: untested)


To gain best performance on your computer's architecture, please consider build the source code. First, you may need Rust tool chain.

$ cd fourth
$ cargo build --release

Binary file will be generated at target/release/fourth, or you can use cargo install --path . to install.

Or you can use Cargo to install Fourth:

$ cargo install fourth

Or you can download binary file form the Release page.


Fourth will read yaml format configuration file from /etc/fourth/config.yaml, and you can set custom path to environment variable FOURTH_CONFIG, here is an minimal viable example:

version: 1
log: info

      - ""
    default: remote

  remote: "tcp://www.remote.example.com:8082" # proxy to remote address

Built-in two upstreams: ban(terminate connection immediately), echo. For detailed configuration, check this example.

Performance Benchmark

Tested on 4C2G server:

Use fourth to proxy to Nginx(QPS of direct connection: ~120000): ~70000 req/s (Command: wrk -t200 -c1000 -d120s --latency http://proxy-server:8081)

Use fourth to proxy to local iperf3: 8Gbps



Fourth is available under terms of Apache-2.0.