Well, if you're all connecting to a public medium, then running a sniffer on your computer will only pick up traffic between your computer and the medium. In order for the sniffer approach to work, you would have to install it on the server that hosts the chat room. There may be a way to fool the site into displaying the IP's if it's written in JS... that would depend on how much you know about javascript injections. I doubt it, though, because most likely that information isn't even seen by the page, but handled by the backend on the server. If that's the case, then there's not much you can do besides break into the backend (aka hack the server). There may be a few loopholes you can use to get their IP's... but it all depends on how the chat room is set up. If you want, PM me the link and I'll tell you if it's possible to find the IP's or not.