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#150 in Network programming

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554 downloads per month
Used in 2 crates (via async-datachannel)

MPL-2.0 license

1.5K SLoC

datachannel-rs   latest doc

Rust wrappers for libdatachannel, a WebRTC Data Channels standalone implementation in C++.


This crate provides two traits that end user must implement, DataChannelHandler and PeerConnectionHandler, which defined all callbacks for RtcPeerConnection and RtcDataChannel structs respectively.

Aforementioned traits are defined as follows:

pub trait DataChannelHandler {
    fn on_open(&mut self) {}
    fn on_closed(&mut self) {}
    fn on_error(&mut self, err: &str) {}
    fn on_message(&mut self, msg: &[u8]) {}
    fn on_buffered_amount_low(&mut self) {}
    fn on_available(&mut self) {}

pub trait PeerConnectionHandler {
    type DCH;

    fn data_channel_handler(&mut self, info: DataChannelInfo) -> Self::DCH;

    fn on_description(&mut self, sess_desc: SessionDescription) {}
    fn on_candidate(&mut self, cand: IceCandidate) {}
    fn on_connection_state_change(&mut self, state: ConnectionState) {}
    fn on_gathering_state_change(&mut self, state: GatheringState) {}
    fn on_data_channel(&mut self, data_channel: Box<RtcDataChannel<Self::DCH>>) {}

Note that all on_* methods have a default no-operation implementation.

The main struct, RtcPeerconnection, takes a RtcConfig (which defines ICE servers) and a instance of PeerConnectionHandler.

Here is the basic workflow:

use datachannel::{DataChannelHandler, DataChannelInfo, PeerConnectionHandler, RtcConfig, RtcPeerConnection};

struct MyChannel;

impl DataChannelHandler for MyChannel {
    fn on_open(&mut self) {
        // TODO: notify that the data channel is ready (optional)

    fn on_message(&mut self, msg: &[u8]) {
        // TODO: process the received message

struct MyConnection;

impl PeerConnectionHandler for MyConnection {
    type DCH = MyChannel;

    /// Used to create the `RtcDataChannel` received through `on_data_channel`.
    fn data_channel_handler(&mut self, _info: DataChannelInfo) -> Self::DCH {

    fn on_data_channel(&mut self, mut dc: Box<RtcDataChannel<Self::DCH>>) {
        // TODO: store `dc` to keep receiving its messages (otherwise it will be dropped)

let ice_servers = vec!["stun:stun.l.google.com:19302"];
let conf = RtcConfig::new(&ice_servers);

let mut pc = RtcPeerConnection::new(&conf, MyConnection)?;

let mut dc = pc.create_data_channel("test-dc", MyChannel)?;
// TODO: exchange `SessionDescription` and `IceCandidate` with remote peer
// TODO: wait for `dc` to be opened (should be signaled through `on_open`)
// ...
// Then send a message
dc.send("Hello Peer!".as_bytes())?;

Complete implementation example can be found in the tests.

See also async-datachannel for an async-based implementation.

Cargo features

  • log (default) Enables logging provided by the log crate (mutually exclusive with tracing).
  • tracing Enables logging provided by the tracing crate (mutally exclusive with log).
  • vendored Builds libdatachannel and its dependencies statically and bundles them in the build (including OpenSSL).
  • media Enables media support through libdatachannel.


Note that CMake is required to compile libdatachannel through datachannel-sys.

Clone the repo recursively:

git clone --recursive https://github.com/lerouxrgd/datachannel-rs.git

Apple macOS

You probably need to set the following environment variables if your build fails with an OpenSSL related error.

export OPENSSL_ROOT_DIR=/usr/local/Cellar/openssl@1.1/1.1.1i/
export OPENSSL_LIBRARIES=/usr/local/Cellar/openssl@1.1/1.1.1i/lib

With the paths of your local OpenSSL installation.


Required dependencies:

# Needed to compile libdatachannel
sudo apt install build-essential cmake pkg-config libssl-dev clang


~241K SLoC