Well when I worked with a Client-Server-System the Server send messages in some pseudo XML, something like this:
So let's assume you have a Player class with an ID, x, y, hp and mp. Your server messages could look like this:
After that you could parse that messages, possibly with a recursive descent parser
You could also send a message "Player(1234,5,8,321,234)", you just have to know how to parse your message for the constructor.
Does that help?