Want to play campaign co-op? Try this...

Open the following ports on your router to the machine you'll be playing UT3 on.

13000 is for debug logging I believe and not needed externally.

77xx is typically 7777 unless someone hosts a different port (whatever you host is all you need)

6500 is needed by gamespy

3783 is needed by gamespy

Then host a campaign and have someone try to join. Let's get some feedback in here with people's results by doing this. I got it to work with JD once, but I have a bunch of ports being forwarded that I shouldn't need.

Yeah, open them on your router.

http://www.portforward.com/english/routers/port_forwarding/routerindex.htm

There is really specific examples there, though they may or may not have you open the right ports.

Just pick your router, then pick UT3 and follow the pretty picture guide.