foo.js

//https://stackoverflow.com/questions/18833920/webrtc-for-realtime-scaling/21103641#21103641
/*
 * Client 1                        Server       Client 2
 * Create an RTC object
 * Create offer
 * set localdescription = offer                 Create RTC object
 * send offer ------------------->       ------>set remote description to offer
 *                                              Create answer
 * local description = answer
 * set remote description<--------       <------send answer
 *
 * This goes both directions:
 * onicecandidate send ---------->       ------>set ICE candidate
 *
 * Connection done!
 */

//
var dc;

// Create a new connection to our signalling server.
var serverConnection = new WebSocket('ws://127.0.0.1:3434');

/**
 * Process any messages we receive from the signalling server.
 */
serverConnection.onmessage = function(message) {
    console.log('Received message from the server');
    var signal = JSON.parse(message.data);

    if(signal.sdp) {
        console.log('Server sent SDP signal');
        peerConnection.setRemoteDescription(new RTCSessionDescription(signal.sdp), function() {
            if(signal.sdp.type == 'offer') {
                peerConnection.createAnswer(descriptionHandler, createAnswerError);
            }
        });
    } else if(signal.ice) {
        console.log('Server sent ICE signal');
        peerConnection.addIceCandidate(new RTCIceCandidate(signal.ice));
    }
}

// Setup our peer config and create a new peer connection.
var peerConnectionConfig = {'iceServers': [{'url': 'stun:stun.services.mozilla.com'}, {'url': 'stun:stun.l.google.com:19302'}]};
var options = {
        optional: [
                    {DtlsSrtpKeyAgreement: true},
                {RtpDataChannels: true} //required for Firefox
            ]
}

var peerConnection = new RTCPeerConnection(peerConnectionConfig, options);

/**
 * When we receive the ICE candidate.
 */
peerConnection.onicecandidate = function(event) {
    console.log('Received ICE candidate:', event);
    if(event.candidate != null) {
        serverConnection.send(JSON.stringify({ 'ice': event.candidate }));
    }
}

/**
 * Create the local offer.
 */
function createOffer() {
    // Create our data channel
    dc = peerConnection.createDataChannel("messages");

    dc.onmessage = function (event) {
        console.log("received: " + event.data);
    };

    dc.onopen = function () {
        console.log("datachannel open");
        var readyState = dc.readyState;
        if (readyState == "open") {
            dc.send("Hello");
        }
    };

    dc.onclose = function () {
        console.log("datachannel close");
    };

    peerConnection.createOffer(descriptionHandler, createOfferErrorHandler);
}

/**
 * Handles description.
 */
function descriptionHandler(description) {
    peerConnection.setLocalDescription(description, function() {
        console.log('Sending description to the server');
        serverConnection.send(JSON.stringify({ 'sdp': description }));
    }, function() { console.log('Set description error') });
}

/**
 *
 */
function createOfferErrorHandler(error) {
    console.log(error);
}

/**
 *
 */
function createAnswerError(error) {
      console.log('createAnswer() error: ', e);
}

/**
 *
 */
function sendMsg() {
    dc.send('Hello!');
}