manifest / datachannel-rs

Rust wrappers for libdatachannel

datachannel-rs  

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

Usage

This crate provides two traits that end user must implement, DataChannel and PeerConnection, that define all available callback methods. Note that all methods have a default no-operation implementation.

Aforementioned traits are defined as follows:

pub trait DataChannel {
    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 PeerConnection {
    type DC;

    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::DC>>) {}
}

Traits implementations are meant to be used through RtcPeerConnection and RtcDataChannel structs.

The main struct, RtcPeerconnection, takes a Config (which defines ICE servers) and a MakeDataChannel instance (a factory trait used internally for on_data_channel callback). Note that this factory trait has a straightforward blanket implementation for Clone types.

Here is the basic workflow:

use datachannel::{Config, DataChannel, PeerConnection, RtcPeerConnection};

struct Chan;
impl DataChannel for Chan {}

struct Conn;
impl PeerConnection for Conn {}

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

let mut pc = RtcPeerConnection::new(&conf, Conn, || Chan)?;

let mut dc = pc.create_data_channel("test-dc", Chan)?;
dc.send("Hello Peer!".as_bytes())?;

Complete implementation example can be found in the tests.

Building

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

Static build

By default libdatachannel will be built and linked dynamically. However there is a static Cargo feature that will build and link it statically (with all its dependencies, including OpenSSL).

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.