Creating servers no one can join.

[Dan Smith]

I seem to have a problem when I host a server, be it listen or dedicated, no one can join it. My friends have tried, but they say it gets stuck trying to connect to the server. I've forwarded all the ports listed in this topic:
http://forums.tripwireinteractive.com/showthread.php?t=30634

And I've created a dedicated server following all these steps:
http://forums.tripwireinteractive.com/showthread.php?t=30579
but to no avail.

Any help would be appreciated.