DataChannel support (with fallback)

This commit adds support for the WebRTC DataChannel API.
This is -- of course -- preliminary. The interface in the future
should not automatically connect to all peers (neither data channel
or video/audio streams).

lib/webrtc.io.js

@@ -56,6 +56,30 @@ var getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || nav
   rtc.numStreams = 0;
   rtc.initializedStreams = 0;
 
+
+  // Reference to the data channels
+  rtc.dataChannels = {};
+
+  // PeerConnection datachannel configuration
+  rtc.dataChannelConfig = {optional: [ {RtpDataChannels: true} ] };
+
+
+  // check whether data channel is supported.
+  rtc.checkDataChannelSupport = function() {
+    try {
+      // raises exception if createDataChannel is not supported
+      var pc = new PeerConnection(rtc.SERVER, rtc.dataChannelConfig);
+      channel = pc.createDataChannel('supportCheck', {reliable: false});
+      channel.close();
+      return true;
+    } catch(e) {
+      return false;
+    }
+  }
+
+  rtc.dataChannelSupport = rtc.checkDataChannelSupport();
+
+
   /**
    * Connects to the websocket server.
    */
@@ -150,7 +174,11 @@ var getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || nav
   };
 
   rtc.createPeerConnection = function(id) {
-    var pc = rtc.peerConnections[id] = new PeerConnection(rtc.SERVER);
+    var config = undefined;
+    if (rtc.dataChannelSupport)
+      config = rtc.dataChannelConfig;
+
+    var pc = rtc.peerConnections[id] = new PeerConnection(rtc.SERVER, config);
     pc.onicecandidate = function(event) {
       if (event.candidate) {
          rtc._socket.send(JSON.stringify({
@@ -174,6 +202,14 @@ var getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || nav
       // TODO: Finalize this API
       rtc.fire('add remote stream', event.stream, id);
     };
+
+    if (rtc.dataChannelSupport) {
+      pc.ondatachannel = function (evt) {
+        console.log('data channel connecting ' + id);
+        rtc.addDataChannel(id, evt.channel);
+      };
+    };
+
     return pc;
   };
 
@@ -261,14 +297,95 @@ var getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || nav
     }
   };
 
-
   rtc.attachStream = function(stream, domId) {
     document.getElementById(domId).src = URL.createObjectURL(stream);
   };
 
+
+  rtc.createDataChannel = function(pcOrId, label) {
+    if (!rtc.dataChannelSupport) {
+      alert('webRTC data channel is not yet supported in this browser,'
+        + ' or you must turn on experimental flags');
+      return;
+    }
+
+    if (typeof(pcOrId) === 'string') {
+      id = pcOrId;
+      pc = rtc.peerConnections[pcOrId];
+    } else {
+      pc = pcOrId;
+      id = undefined;
+      for (var key in rtc.peerConnections) {
+        if (rtc.peerConnections[key] === pc)
+          id = key;
+      }
+    }
+
+    if (!id)
+      throw new Error ('attempt to createDataChannel with unknown id');
+
+    if (!pc || !(pc instanceof PeerConnection))
+      throw new Error ('attempt to createDataChannel without peerConnection');
+
+    // need a label
+    label = label || 'fileTransfer' || String(id);
+
+    // chrome only supports reliable false atm.
+    options = {reliable: false};
+
+    try {
+      console.log('createDataChannel ' + id);
+      channel = pc.createDataChannel(label, options);
+    } catch (error) {
+      console.log('seems that DataChannel is NOT actually supported!');
+      throw error;
+    }
+
+    return rtc.addDataChannel(id, channel);
+  }
+
+  rtc.addDataChannel = function(id, channel) {
+
+    channel.onopen = function() {
+      console.log('data stream open ' + id)
+      rtc.fire('data stream open', channel);
+    }
+
+    channel.onclose = function(event) {
+      delete rtc.dataChannels[id];
+      console.log('data stream close ' + id)
+      rtc.fire('data stream close', channel);
+    }
+
+    channel.onmessage = function(message) {
+      console.log('data stream message ' + id);
+      console.log(message);
+      rtc.fire('data stream data', channel, message.data);
+    }
+
+    channel.onerror = function(err) {
+      console.log('data stream error ' + id + ': ' + err);
+      rtc.fire('data stream error', channel, err);
+    }
+
+    // track dataChannel
+    rtc.dataChannels[id] = channel;
+    return channel;
+  };
+
+  rtc.addDataChannels = function() {
+    if (!rtc.dataChannelSupport)
+      return;
+
+    for (var connection in rtc.peerConnections)
+      rtc.createDataChannel(connection);
+  };
+
+
   rtc.on('ready', function() {
     rtc.createPeerConnections();
     rtc.addStreams();
+    rtc.addDataChannels();
     rtc.sendOffers();
   });