I am attempting to write a multiplayer realtime game and run it on CloudBees (the customer side is definitely an applet, the server side a java web application). Can you really provide the server permission to pay attention on another port? (ie therefore the server-side code can produce a ServerSocket on that port and also the client side code can produce a Socket for connecting and contact the server)

Although it might be possible it is extremely tricky because the available port will probably change as the application moves around. On the top of the - you should locate the address from the demonstration of where your application is running (ie some type of dynamic directory) - so type of tricky. The net routing layer does all of this for you personally - but presumes http or similar (you should use "lengthy poll" and an association open from an applet - this might work similarly, with a few work).