libdatachannel

libdatachannel - C/C++ WebRTC DataChannels

libdatachannel is a standalone implementation of WebRTC DataChannels in C++17 with C bindings for POSIX platforms and Microsoft Windows. It enables direct connectivity between native applications and web browsers without the pain of importing the entire WebRTC stack. Its API is modelled as a simplified version of the JavaScript WebRTC API, in order to ease the design of cross-environment applications.

This projet is originally inspired by librtcdcpp, however it is a complete rewrite from scratch, because the messy architecture of librtcdcpp made solving its implementation issues difficult.

The connectivity can be provided through my ad-hoc ICE library libjuice as submodule or through libnice. The security layer can be provided through GnuTLS or OpenSSL.

Licensed under LGPLv2, see LICENSE.

Compatibility

The library aims at fully implementing WebRTC SCTP DataChannels (draft-ietf-rtcweb-data-channel-13) over DTLS/UDP (RFC7350 and RFC8261) with ICE (RFC8445). It has been tested to be compatible with Firefox and Chromium. It supports IPv6 and Multicast DNS candidates resolution (draft-ietf-rtcweb-mdns-ice-candidates-03) provided the operating system also supports it.

Dependencies

• GnuTLS: https://www.gnutls.org/ or OpenSSL: https://www.openssl.org/

Optional:

• libnice: https://nice.freedesktop.org/ (substituable with libjuice)

Submodules:

• usrsctp: https://github.com/sctplab/usrsctp
• libjuice: https://github.com/paullouisageneau/libjuice

Building

Building with CMake (preferred)

$ git submodule update --init --recursive
$ mkdir build
$ cd build
$ cmake -DUSE_JUICE=1 -DUSE_GNUTLS=1 ..
$ make

Building directly with Make

$ git submodule update --init --recursive
$ make USE_JUICE=1 USE_GNUTLS=1

Example

In the following example, note the callbacks are called in another thread.

Signal a PeerConnection

#include "rtc/rtc.hpp"

rtc::Configuration config;
config.iceServers.emplace_back("mystunserver.org:3478");

auto pc = make_shared<rtc::PeerConnection>(config);

pc->onLocalDescription([](const rtc::Description &sdp) {
    // Send the SDP to the remote peer
    MY_SEND_DESCRIPTION_TO_REMOTE(string(sdp));
});

pc->onLocalCandidate([](const rtc::Candidate &candidate) {
    // Send the candidate to the remote peer
    MY_SEND_CANDIDATE_TO_REMOTE(candidate.candidate(), candidate.mid());
});

MY_ON_RECV_DESCRIPTION_FROM_REMOTE([pc](string sdp) {
    pc->setRemoteDescription(rtc::Description(sdp));
});

MY_ON_RECV_CANDIDATE_FROM_REMOTE([pc](string candidate, string mid) {
    pc->addRemoteCandidate(rtc::Candidate(candidate, mid));
});

Observe the PeerConnection state

pc->onStateChange([](PeerConnection::State state) {
    cout << "State: " << state << endl;
});

pc->onGatheringStateChange([](PeerConnection::GatheringState state) {
    cout << "Gathering state: " << state << endl;
});

Create a DataChannel

auto dc = pc->createDataChannel("test");
dc->onOpen([]() {
    cout << "Open" << endl;
});
dc->onMessage([](const variant<binary, string> &message) {
    if (holds_alternative<string>(message)) {
        cout << "Received: " << get<string>(message) << endl;
    }
});

Receive a DataChannel

shared_ptr<rtc::DataChannel> dc;
pc->onDataChannel([&dc](shared_ptr<rtc::DataChannel> incoming) {
    dc = incoming;
    dc->send("Hello world!");
});

See test/connectivity.cpp for a complete local connection example.