LAN chat server?

[Timothy Luoma]

I'm looking for a simple chat server (ala AIM) that I can run on 
FreeBSD to allow users on our LAN to communicate with one another.

What I need:

[  ] free, no-ad client apps for WinXP and Mac

[  ] ability to transfer files (drag and drop, ideally)

[  ] server to run on 5.3 (no-gui/x)

I did some looking around and it looks like Jabber is one possibility, 
but I don't know much about it.

If Jabber, which do you recommend?

If not Jabber, what else?

Thanks for your suggestions.

TjL