#websocket #tokio

bin+lib yarws

Yet Another Rust WebSocket library

6 releases

0.3.0 May 1, 2020
0.2.1 Apr 28, 2020
0.1.2 Apr 19, 2020

#51 in WebSocket

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86 downloads per month

MIT license



WebSocket protocol implementation based on Tokio runtime. For building WebSocket server or client.

yarws = Yet Another Rust WebSocket library

Tls (wss:// enpoints) are supported in connect (since version 0.2.0).

Lib is passing all autobahn tests. Including those for compressed messages. Per message deflate is implemented for incoming messages. Lib can receive compressed messages. Currently all outgoing messages are sent uncompressed.



    let addr = "";
    let mut listener = Server::new(addr).bind().await?;
    while let Some(mut socket) = listener.accept().await {
        tokio::spawn(async move {
            while let Some(msg) = socket.recv().await {

This is an example of echo server. We are replying with the same message on each incoming message. Second line starts listening for WebSocket connections on an ip:port. Each client is represented by Socket returned from accept. For each client we are looping while messages arrive and replying with the same message. For the complete echo server example please take a look at examples/echo_server.rs.


    let url = "ws://";
    let mut socket = Client::new(url).connect().await?;
    while let Some(msg) = socket.recv().await {

This is example of an echo client. [connect] method returns Socket which is used to send and receive messages. Looping on recv returns each incoming message until socket is closed. Here in loop we reply with the same message. For the complete client example refer to examples/client.rs.


Run client with external echo server.

cargo run --example client -- ws://echo.websocket.org

Client will send few messages of different sizes and expect to get the same in return. If everything went fine will finish without error.

To run same client on our server. First start server:

cargo run --example echo_server

Then in other terminal run client:

cargo run --example client

If it is in trace log mode server will log type and size of every message it receives.

websocat test tool

You can use websocat to connect to the server and test communication. First start server:

cargo run --example echo_server

Then in other terminal run websocat:

websocat -E --linemode-strip-newlines ws://

Type you message press enter to send it and server will reply with the same message. For more exciting server run it in with reverse flag:

cargo run --bin echo_server -- --reverse

and than use websocat to send text messages.

Autobahn tests

Ensure that you have wstest autobahn-testsuite test tool installed:

pip install autobahntestsuite

Start echo_server:

cargo run --bin echo_server

In another terminal run server tests and view results:

cd autobahn
wstest -m fuzzingclient
open reports/server/index.html

For testing client implementation first start autobahn server suite:

wstest -m fuzzingserver

Then in another terminal run client tests and view results:

cargo run --bin autobahn_client
open autobahn/reports/client/index.html

For development purpose there is automation for running autobahn test suite and showing results:

cargo run --bin autobahn_server_test

you can use run that in development on every file change with cargo-watch:

cargo watch -x 'run --bin autobahn_server_test'

Chat server example

Simple example of server accepting text messages and distributing them to the all connected clients. First start chat server:

cargo run --bin chat_server

Then in browser development console connect to the server and send chat messages:

var socket = new WebSocket('ws://');
var msgNo = 0;
var interval;
socket.addEventListener('open', function (event) {
    socket.send("new client");
    interval = setInterval(function() {
        socket.send("message: " + msgNo);
    }, 1000);
socket.addEventListener('message', function (event) {
    console.log('chat', event.data);
socket.addEventListener('close', function (event) {

Start multiple browser tabs with the same code running. You can disconnect from the server with: socket.close();.


WebSocket Protocol IETF RFC 6455 MDN writing WebSocket servers

License: MIT


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