Messing with network via java...

Hi Guys : I remeber in the labs one time some guy kept
making these pops appear on my machine. He was
on another computer on the same network.

How is this done ? Im an advanced Java developer and software
designer, but dont have alot of concrete network
hacking experience. I need to do this for an application
at work and was hoping I could integrate this silly network hack
with swing and Java if possible - but at the very least Id like to
know how to "force" a pop up message to appear on a computer
on the same network. NOTE : Im not worried at all about network
security or firewalls so a solution for a low security network
will do.

Can some body help me out ?

Some kind of process would have to run on all machines where these popups should appear, which listens for network requests and then show the dialog. This is rather annoying, though, so make sure your users won't mind.

If what you saw was on Windows, then the admin probably used the "net send" feature, which does exactly what you decribe.