Hello everyone. I don't normally post on fora but I am really stuck!

THE PROBLEM.

I need to set up a server with multiple clients talking to each other. Sounds easy? Just a matter of setting up some Sockets with DataInputStream/DataOutputStream and some threads. Unfortunately I am having difficulty with this. Here are the steps I am taking to create my application:


Steps:
Get a client and a server to talk to each other. (I can do this)
Get multiple clients talking independently to a server. (I can do this)
Get multiple clients talking to each other via a server. (CAN'T GET PAST THIS STEP!)
As above, but with clients allocated turns to post in round-robin fashion.
As above, but with client input validated.


If someone could give me advice or a pointer to a resource to solve my problem I would be very grateful. For example: should I be using a Multicast rather than DataOutputStream to send messages from a server to simultaneous multiple clients?

cheers
Craig W