tokio-websockets

High performance, strict, tokio-util based WebSockets implementation.

Why use tokio-websockets?

• Built with tokio-util, intended to be used with tokio from the ground up
• Minimal dependencies: The base only requires:
  • tokio, tokio-util, bytes, futures-core, futures-sink, simdutf8
  • SHA1 backend, e.g. sha1_smol (see Feature flags)
• Big selection of features to tailor dependencies to any project (see Feature flags)
• SIMD support: AVX512, AVX2, SSE2, NEON or AltiVec for frame (un)masking and accelerated UTF-8 validation
• Strict conformance with the WebSocket specification, passes the Autobahn test suite without relaxations by default
• TLS support
• Reusable TLS connectors
• Uses widely known crates from the ecosystem for types, for example Uri from http in the client
• Cheaply clonable messages due to Bytes as payload storage
• Tuned for performance (see the benchmarks)

Feature flags

Feature flags in tokio-websockets are added to allow tailoring it to your needs.

• The simd feature flag is deprecated and has no effect. SIMD support is detected at runtime now rather than opting in at compile time
• The nightly feature when using a nightly compiler will enable AVX512, NEON (on 32-bit ARM) or AltiVec accelerated masking
• client enables a tiny client implementation
• server enables a tiny server implementation

TLS is supported via any of the following feature flags:

• native-tls for a tokio-native-tls backed implementation
• rustls-webpki-roots for a tokio-rustls backed implementation with webpki-roots
• rustls-native-roots for a tokio-rustls backed implementation with rustls-native-certs
• rustls-platform-verifier for a tokio-rustls backed implementation with rustls-platform-verifier
• rustls-bring-your-own-connector for a tokio-rustls backed implementation that requires you to create your own Connector::Rustls - the Connector::new method will return a plain connector

The rustls-*-roots and rustls-platform-verifier features require a crypto provider for rustls. You can either enable the aws_lc_rs (optionally also FIPS-compliant via the fips feature) or ring features to use these crates as the providers and then use TlsConnector::new(), or bring your own with TlsConnector::new_rustls_with_crypto_provider().

One SHA1 implementation is required, usually provided by the TLS implementation:

• ring or aws_lc_rs are used if the ring or aws_lc_rs features are enabled (recommended when rustls is used)
• The openssl feature will use openssl, usually preferred on most Linux/BSD systems with native-tls
• The sha1_smol feature can be used as a fallback if no TLS is needed

The client feature requires enabling one random number generator:

• fastrand can be used as a PRNG
• getrandom can be used as a cryptographically secure RNG
• rand can be used as an alternative to fastrand and should be preferred if it is already in the dependency tree

Example

This is a simple WebSocket echo server without any proper error handling.

More examples can be found in the examples folder.

use futures_util::{SinkExt, StreamExt};
use http::Uri;
use tokio::net::TcpListener;
use tokio_websockets::{ClientBuilder, Error, Message, ServerBuilder};

#[tokio::main]
async fn main() -> Result<(), Error> {
  let listener = TcpListener::bind("127.0.0.1:3000").await?;

  tokio::spawn(async move {
    while let Ok((stream, _)) = listener.accept().await {
      let (_request, mut ws_stream) = ServerBuilder::new()
        .accept(stream)
        .await?;

      tokio::spawn(async move {
        // Just an echo server, really
        while let Some(Ok(msg)) = ws_stream.next().await {
          if msg.is_text() || msg.is_binary() {
            ws_stream.send(msg).await?;
          }
        }

        Ok::<_, Error>(())
      });
    }

    Ok::<_, Error>(())
  });

  let uri = Uri::from_static("ws://127.0.0.1:3000");
  let (mut client, _) = ClientBuilder::from_uri(uri).connect().await?;

  client.send(Message::text("Hello world!")).await?;

  while let Some(Ok(msg)) = client.next().await {
    if let Some(text) = msg.as_text() {
      assert_eq!(text, "Hello world!");
      // We got one message, just stop now
      client.close().await?;
    }
  }

  Ok(())
}

MSRV

The current MSRV for all feature combinations is Rust 1.79.

Caveats / Limitations / ToDo

WebSocket compression is currently unsupported.