tocat

A socat-inspired relay built on tokio. tocat connects two endpoints (sockets, files, subprocesses, stdio, etc.) and copies bytes between them in both directions. Unlike socat, connections can be described in a TOML config file with editor completion and validation, and the bytes in flight can be passed through a pipeline of plugins.

$ cargo install --locked tocat

$ tocat - tcp:localhost:9000
$ tocat tcp-listen:9000,fork tcp:localhost:8080
$ tocat tcp-listen:8080,fork tee,format=hex tcp:example.com:80
$ tocat -f tcp-listen:8080,fork -t tcp:example.com:80 -p 'throttle,rate=1MiB'

A run is a source, a sink, and an optional pipeline of plugins between them. The outer positional arguments are the endpoints and anything between them is a pipeline entry; --from and --to fill the same two slots, and -p adds an entry wherever the endpoints came from.

The same run can live in a tocat.toml, which tocat finds and merges with the command line, the command line winning:

source = "tcp-listen:9000,fork"
sink = "tcp:localhost:8080"

[[plugin]]
name = "tee"
format = "hex"

Plugins

Plugins are cargo features and all of them are on by default, so subtracting one means turning the defaults off and naming what you want back:

$ cargo install --locked tocat --no-default-features --features tee,rate

all-plugins-no-wasm is the one worth knowing: it gives everything except the WebAssembly host, which is most of the build time.

tocat --list-plugins prints what your binary was actually built with.

Bytes can also be passed through a WebAssembly module, written in Rust with tocat-wasm-sdk or in C or C++ with the CMake SDK in the repository. A guest imports nothing at all: no clock, no files, no sockets.

Documentation

The user guide, the plugin API and the design notes are an mdbook under docs/ in the repository.

License

MIT or Apache-2.0, at your option.