code: function onClientConnection(clientSocket, onConnectionCallback) {
  
    var elementsEventHandler = new ElementsEventHandler(clientSocket);
    elementsEventHandler.session = clientSocket.handshake.session;
    debug("client connection");
    clientSocket.trigger = trigger.bind(clientSocket);
    //clientSocket.broadcast.trigger = broadcast.bind(clientSocket);
    clientSocket.on.message = onmessage.bind(clientSocket);
    onConnectionCallback(null, elementsEventHandler);
    elementsEventHandler.on("disconnect", function deleteElementsEventHandler() {
      elementsEventHandler = undefined;
    });
  }
docs: Handles a new myelements client connection.
  
  @param {socket}. client socket for the new connection
  @param {Function} onConnectionCallback. called after socket.io connection event
  - @param {Error} err. Null if nothing bad happened.
  - @param {ElementsEventHandler} elementsEventHandler. An instance
  of myelements client's event handler.