To test, do: java Client after java Server.
First register by clicking register at the bottom of the window. There is no confirmation after unregistering. To select the group to send the message to, select the group in the window then press set group. To create more groups that everyone will see, press create group.
Text commands are available:
//originally I had the idea of being a member of multiple groups. It might work but I haven't tested it. SETGROUPS
CREATEGROUP
REGISTER
UNREGISTER