Java Chat Username Registration Error.

Okay, I've been developing a Java chatroom, and I want to, when someone enters the chatroom, have the user register his username with the server. When I do that, it lets people know who's in the chatroom. Whenever I try it, it makes some crazy unstoppable loop of foreverness.
[285 byte] By [KKera] at [2007-11-27 7:36:44]
# 1
You're probably sending the username back to that user and so starting a broadcast storm.
ejpa at 2007-7-12 19:17:18 > top of Java-index,Core,Core APIs...