code: function _send(msg, clients) {
          var id = _nextMsgId++,
              result = new $.Deferred();
  
          // broadcast if there are no specific clients
          clients = clients || getConnectionIds();
          msg.id = id;
          _responseDeferreds[id] = result;
          _transport.send(clients, JSON.stringify(msg));
          return result.promise();
      }
docs: @private
  Dispatches a message to the remote protocol handler via the transport.
  
  @param {Object} msg The message to send.
  @param {number|Array.<number>} idOrArray ID or IDs of the client(s) that should
  receive the message.
  @return {$.Promise} A promise that's fulfilled when the response to the message is received.