Hi Christian,
On the server side, you need something that can negotiate the WebSocket handshake, handle the incoming data and frame the outgoing data properly. There are several implementations available in various languages (
http://en.wikipedia.org/wiki/WebSocket#Server_side), but the most popular these days is Socket.io. Socket.io also provides a client side library and several fallback mechanisms. No matter which backend you go with, the logic of the application is still up to you. You have to figure out what data you want to pass and what you are going to do with it.
My book doesn't talk about specific server implementations. It focuses on the JavaScript API on the client side and the protocol itself.
Scott