socket.io - iPad always gets a timeout, although it is connected

I have a simple chat app with node.js and socket.io: tutorial full code

It works perfectly if the clients enters the website from a PC. If the client uses a IPad (ios 5.1/ latest Chrome / safari) it only works sometimes. Most of the time the webpage is loaded, then the iPad connects, but it takes so long that the server closes the connection. Then the iPad gets a new connection, but cannot really initialize a session. It periodically is disconnected and tries to reconnect again.

Here the protocoll of socket.io:

client code:

socket = io.connect(http://42.58.240.427:4000);
socket.on('connect', function(){

  send('init');
});

server code:

io.sockets.on('connection', function (socket) {

socket.on('init', function(){

    console.log("Good morning new User");
});


socket.on('disconnect', function(){

    requesthandler['disconnect'](socket, io);

});