Use only xhr polling

node/server.js

@@ -153,6 +153,10 @@ async.waterfall([
     //init socket.io and redirect all requests to the MessageHandler
     var io = socketio.listen(app);
     
+    //this is only a workaround to ensure it works with all browers behind a proxy
+    //we should remove this when the new socket.io version is more stable
+    io.set('transports', ['xhr-polling']);
+    
     var padMessageHandler = require("./PadMessageHandler");
     var timesliderMessageHandler = require("./TimesliderMessageHandler");