peerjs/lib/negotiator.js

/**
 * Manages all negotiations between Peers.
 */
var Negotiator = {
  pcs: {
    data: {},
    media: {}
  }, // type => {peerId: {pc_id: pc}}.
  //providers: {}, // provider's id => providers (there may be multiple providers/client.
  queue: [] // connections that are delayed due to a PC being in use.
}

Negotiator._idPrefix = 'pc_';

/** Returns a PeerConnection object set up correctly (for data, media). */
Negotiator.startConnection = function(connection, options) {
  var pc = Negotiator._getPeerConnection(connection, options);

  if (connection.type === 'media' && options._stream) {
    // Add the stream.
    pc.addStream(options._stream);
  }

  // Set the connection's PC.
  connection.pc = pc;
  // What do we need to do now?
  if (options.originator) {
    if (connection.type === 'data') {
      // Create the datachannel.
      var config = {};
      if (util.supports.reliable && !options.reliable) {
        // If we have canonical reliable support...
        config = {maxRetransmits: 0}
      }
      var dc = pc.createDataChannel(connection.label, config);
      connection.initialize(dc);
    }

    if (!util.supports.onnegotiationneeded) {
      Negotiator._makeOffer(connection);
    }
  } else {
    Negotiator.handleSDP('OFFER', connection, options.sdp);
  }
}

Negotiator._getPeerConnection = function(connection, options) {
  if (!Negotiator.pcs[connection.type]) {
    util.error(connection.type + ' is not a valid connection type. Maybe you overrode the `type` property somewhere.');
  }

  if (!Negotiator.pcs[connection.type][connection.peer]) {
    Negotiator.pcs[connection.type][connection.peer] = {};
  }
  var peerConnections = Negotiator.pcs[connection.type][connection.peer];

  var pc;
  // Not multiplexing while FF and Chrome have not-great support for it.
  /*if (options.multiplex) {
    ids = Object.keys(peerConnections);
    for (var i = 0, ii = ids.length; i < ii; i += 1) {
      pc = peerConnections[ids[i]];
      if (pc.signalingState === 'stable') {
        break; // We can go ahead and use this PC.
      }
    }
  } else */
  if (options.pc) { // Simplest case: PC id already provided for us.
    pc = Negotiator.pcs[connection.type][connection.peer][options.pc];
  }

  if (!pc || pc.signalingState !== 'stable') {
    pc = Negotiator._startPeerConnection(connection);
  }
  return pc;
}

/*
Negotiator._addProvider = function(provider) {
  if ((!provider.id && !provider.disconnected) || !provider.socket.open) {
    // Wait for provider to obtain an ID.
    provider.on('open', function(id) {
      Negotiator._addProvider(provider);
    });
  } else {
    Negotiator.providers[provider.id] = provider;
  }
}*/


/** Start a PC. */
Negotiator._startPeerConnection = function(connection) {
  util.log('Creating RTCPeerConnection.');

  var id = Negotiator._idPrefix + util.randomToken();
  var optional = {};

  if (connection.type === 'data' && !util.supports.reliable) {
    optional = {optional: [{RtpDataChannels: true}]};
  } else if (connection.type === 'media') {
    // Interop req for chrome.
    optional = {optional: [{DtlsSrtpKeyAgreement: true}]};
  }

  var pc = new RTCPeerConnection(connection.provider.options.config, optional);
  Negotiator.pcs[connection.type][connection.peer][id] = pc;

  Negotiator._setupListeners(connection, pc, id);

  return pc;
}

/** Set up various WebRTC listeners. */
Negotiator._setupListeners = function(connection, pc, pc_id) {
  var peerId = connection.peer;
  var connectionId = connection.id;
  var provider = connection.provider;

  // ICE CANDIDATES.
  util.log('Listening for ICE candidates.');
  pc.onicecandidate = function(evt) {
    if (evt.candidate) {
      util.log('Received ICE candidates for:', connection.peer);
      provider.socket.send({
        type: 'CANDIDATE',
        payload: {
          candidate: evt.candidate,
          type: connection.type,
          connectionId: connection.id
        },
        dst: peerId,
      });
    }
  };

  pc.oniceconnectionstatechange = function() {
    switch (pc.iceConnectionState) {
      case 'disconnected':
      case 'failed':
        util.log('iceConnectionState is disconnected, closing connections to ' + peerId);
        connection.close();
        break;
      case 'completed':
        pc.onicecandidate = util.noop;
        break;
    }
  };

  // Fallback for older Chrome impls.
  pc.onicechange = pc.oniceconnectionstatechange;

  // ONNEGOTIATIONNEEDED (Chrome)
  util.log('Listening for `negotiationneeded`');
  pc.onnegotiationneeded = function() {
    util.log('`negotiationneeded` triggered');
    if (pc.signalingState == 'stable') {
      Negotiator._makeOffer(connection);
    } else {
      util.log('onnegotiationneeded triggered when not stable. Is another connection being established?');
    }
  };

  // DATACONNECTION.
  util.log('Listening for data channel');
  // Fired between offer and answer, so options should already be saved
  // in the options hash.
  pc.ondatachannel = function(evt) {
    util.log('Received data channel');
    var dc = evt.channel;
    var connection = provider.getConnection(peerId, connectionId);
    connection.initialize(dc);
  };

  // MEDIACONNECTION.
  util.log('Listening for remote stream');
  pc.onaddstream = function(evt) {
    util.log('Received remote stream');
    var stream = evt.stream;
    provider.getConnection(peerId, connectionId).addStream(stream);
  };
}

Negotiator.cleanup = function(connection) {
  util.log('Cleaning up PeerConnection to ' + connection.peer);

  var pc = connection.pc;

  if (!!pc && (pc.readyState !== 'closed' || pc.signalingState !== 'closed')) {
    pc.close();
    connection.pc = null;
  }
}

Negotiator._makeOffer = function(connection) {
  var pc = connection.pc;
  pc.createOffer(function(offer) {
    util.log('Created offer.');

    if (!util.supports.reliable && connection.type === 'data' && connection.reliable) {
      offer.sdp = Reliable.higherBandwidthSDP(offer.sdp);
    }

    pc.setLocalDescription(offer, function() {
      util.log('Set localDescription: offer', 'for:', connection.peer);
      connection.provider.socket.send({
        type: 'OFFER',
        payload: {
          sdp: offer,
          type: connection.type,
          label: connection.label,
          reliable: connection.reliable,
          serialization: connection.serialization,
          metadata: connection.metadata,
          connectionId: connection.id
        },
        dst: connection.peer,
      });
    }, function(err) {
      connection.provider.emit('error', err);
      util.log('Failed to setLocalDescription, ', err);
    });
  }, function(err) {
    connection.provider.emit('error', err);
    util.log('Failed to createOffer, ', err);
  }, connection.options.constraints);
}

Negotiator._makeAnswer = function(connection) {
  var pc = connection.pc;

  pc.createAnswer(function(answer) {
    util.log('Created answer.');

    if (!util.supports.reliable && connection.type === 'data' && connection.reliable) {
      answer.sdp = Reliable.higherBandwidthSDP(answer.sdp);
    }

    pc.setLocalDescription(answer, function() {
      util.log('Set localDescription: answer', 'for:', connection.peer);
      connection.provider.socket.send({
        type: 'ANSWER',
        payload: {
          sdp: answer,
          type: connection.type,
          connectionId: connection.id
        },
        dst: connection.peer
      });
    }, function(err) {
      connection.provider.emit('error', err);
      util.log('Failed to setLocalDescription, ', err);
    });
  }, function(err) {
    connection.provider.emit('error', err);
    util.log('Failed to create answer, ', err);
  });
}

/** Handle an SDP. */
Negotiator.handleSDP = function(type, connection, sdp) {
  sdp = new RTCSessionDescription(sdp);
  var pc = connection.pc;

  util.log('Setting remote description', sdp);
  pc.setRemoteDescription(sdp, function() {
    util.log('Set remoteDescription:', type, 'for:', connection.peer);

    if (type === 'OFFER') {
      Negotiator._makeAnswer(connection);
    }
  }, function(err) {
    connection.provider.emit('error', err);
    util.log('Failed to setRemoteDescription, ', err);
  });
}

/** Handle a candidate. */
Negotiator.handleCandidate = function(connection, ice) {
  var candidate = ice.candidate;
  var sdpMLineIndex = ice.sdpMLineIndex;
  connection.pc.addIceCandidate(new RTCIceCandidate({
    sdpMLineIndex: sdpMLineIndex,
    candidate: candidate
  }));
  util.log('Added ICE candidate for:', connection.peer);
}