Very Computer

OK I have a very interesting question which I hope someone could answer
for me.
About a year ago there was a student at my University had a complied a
program under UNIX which works like USERLIST on a Novell network. I use
to use this a lot to find where my friends are logged on. He made it
publically usable but now he's gone and won't tell how its did it.
Do this have something to do with SPX/IPX and TCPIP packets ?

Any info would be great.

Aamir