rtcpeerconnection

RTCPeerConnection

What is this?

A tiny browser module that gives normalizes and simplifies the API for WebRTC peer connections.

It gives us a cleaner (cross-browser) way to handle offer/answer and is based on an event emitter.

If you're not using browserify or you want AMD support use rtcpeerconnection.bundle.js.

It also applies the SDP hack for lifting data transfer speed limits imposed by chrome by default. It modifies the "AS" or application specific maximum bandwidth setting from 30 kilobits / sec to 100 Mbps. This is really handy for file transfers, etc. It can be disabled by passing {sdpHack: false} as part of your config as passed in the first argument.

Installing

npm install rtcpeerconnection

How to use it

Instantiation

Instantiation takes the same options as a normal peer connection constructor:

var PeerConnection = require('rtcpeerconnection');


// init it like a normal peer connection object
// passing in ice servers/constraints the initial server config
// also takes a couple other options:
// sdpHack: false (to not use the SDP hack as described above)
// debug: true (to log out all emitted events)
var pc = new PeerConnection({config servers as usual}, {constraints as to regular PC});

Events

Unlike stock Peer Connections this inherits from a generic event emitter. Powered by WildEmitter which has a very familiar API if you're used to node.js/jQUery/Backbone but also includes a wildcard handler so you can easily debug events. Just do emitter.on('*') to log them out or whatnot.

But instead of doing pc.onicecandidate = function () {} on a peer connection you listen for events like this:

// ice candidates
pc.on('ice', function (candidate) {
    // it's your job to send these to someone
    connection.send('ice', candidate);
});

// you can listen for end of candidates (not particularly useful)
pc.on('endOfCandidates', function () {
    // no more ice candidates
});

// remote stream added
pc.on('streamAdded', function (stream) {
    // do something with the remote stream
    // probably attach it to a <video> element
    // and play it.
});

// remote stream removed
pc.on('streamRemoved', function (stream) {
    // remote stream removed
    // now you could hide/disable removed video
});

// you can chose to listen for events for 
// offers and answers instead, if you prefer 
pc.on('answer', function (answer) { ... });
pc.on('offer', function (offer) { ... });

// on peer connection close
pc.on('close', function () { ... });

Methods

Note that all callbacks follow the "error first" convention. Meaning, rather than pass a success and fail callback, you pass a single callback.

If there is an error, the first argument passed to the callback will be a truthy value (the error itself).

The whole offer/answer cycle looks like this:

// assumptions
var pc = new PeerConnection(config, constraints);
var connection = new RealTimeConnection(); // could be socket.io or whatever


// create an offer
pc.offer(function (offer) {
    connection.send('offer', offer)
});

// you can also optionally pass in constraints
// when creating an offer.
pc.offer({
        mandatory: {
            OfferToReceiveAudio: true,
            OfferToReceiveVideo: false
        }
    }, 
    function (err, offer) {
        if (!err) connection.send('offer', offer);
    }
);

// when you recieve an offer, you can answer
// with various options
connection.on('offer', function (offer) {
    // let the peerconnection handle the offer
    // by calling handleOffer
    pc.handleOffer(offer, function (err) {
        if (err) {
            // handle error
            return;
        }

        // you can just call answer
        pc.answer(function (err, answer) {
            if (!err) connection.send('answer', answer);
        });

        // you can call answer with contstraints
        pc.answer(MY_CONSTRAINTS, function (err, answer) {
            if (!err) connection.send('answer', answer);
        });    

        // or you can use one of the shortcuts answers

        // for video only
        pc.answerVideoOnly(function (err, answer) { ... });

        // and audio only
        pc.answerAudioOnly(function (err, answer) { ... });
    }); 
});

// when you get an answer, you just call
// handleAnswer
connection.on('answer', function (answer) {
    pc.handleAnswer(answer);
});

// the only other thing you have to do is listen, transmit, and process ice candidates

// you have to send them when generated
pc.on('ice', function (candidate) {
    connection.send('ice', candidate);
});

// process incoming ones
connection.on('ice', function (candidate) {
    pc.processIce(candidate);
});

That's it!

More

If you want higher level functionality look at SimpleWebRTC that uses this library.

License

MIT

Credits

If you like this, follow: @HenrikJoreteg on twitter.