To start with Socket.IO I suggest you read first the example on the main page:
http://socket.io/
On the server side, read the "How to use" on the GitHub source page:
https://github.com/Automattic/socket.io
And on the client side:
https://github.com/Automattic/socket.io-client
Finally you need to read this great tutorial:
http://howtonode.org/websockets-socketio
Hint: At the end of this blog post, you will have some links pointing on source code that could be some help.