Hey Everyone,
This is my first post. Recently, I have been working on an instant messenger program in java. I have created the networking part of the client, and I have almost finished the server side. I know the program works and I am allowed to send messages, but now I am thinking about adding a feature that lets the user see who else is connected to the server, but i can not think of how to do this. Anyone have any ideas?

Have the clients "register", and have the server keep a list. What's the problem?