# Fourth > Hey, now we are on level 4! [![](https://img.shields.io/crates/v/fourth)](https://crates.io/crates/fourth) [![CI](https://img.shields.io/github/workflow/status/kernelerr/fourth/Rust)](https://github.com/KernelErr/fourth/actions/workflows/rust.yml) **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. ## Features - Listen on specific port and proxy to local or remote port - SNI-based rule without terminating TLS connection - Allow KCP inbound(warning: untested) ## Installation To gain best performance on your computer's architecture, please consider build the source code. First, you may need [Rust tool chain](https://rustup.rs/). ```bash $ 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: ```bash $ cargo install fourth ``` ## Configuration Fourth will read yaml format configuration file from `/etc/fourth/config.yaml`, here is an example: ```yaml version: 1 log: info servers: example_server: listen: - "0.0.0.0:443" - "[::]:443" tls: true # Enable TLS features like SNI sni: proxy.example.com: proxy www.example.com: nginx default: ban relay_server: listen: - "127.0.0.1:8081" default: remote upstream: nginx: "127.0.0.1:8080" proxy: "127.0.0.1:1024" remote: "www.remote.example.com:8082" # proxy to remote address ``` Built-in two upstreams: ban(terminate connection immediately), echo ## Thanks - [tokio_kcp](https://github.com/Matrix-Zhang/tokio_kcp) ## License Fourth is available under terms of Apache-2.0.