You know if I knew how to do that whole hosting thing that L4D and Modern Warfare 2 does, where you "host" a "local" server without port forwarding (has something to do with NAT (Network Address Translation, self explanatory)), I'd do that instead. I've been thinking about me and maybe some other people getting some dedicated servers up some time after the Community is released for those people who can't port forward for some reason or another.
It's actually not NAT traversal, it's just a single server which "serves" people
basically when you "host" a lobby, you're really just getting limited control of a big server. However, the server itself costs money, and for a small community like this you might as well just host a dedicated server yourself.
Edit : FYI, it's not a very good idea for you to do NAT traversal it in TCP. You can bypass port forwarding by doing some hole punching, but since TCP is a connection based protocal, you're going to have a tough time getting it to work.
Basically, as far as I know, how stuff like hamachi works in TCP, there's a single server in the middle between the host and the client. The host connects to the Hamachi server, and so does the client. Then any data that must be transferred from the Server to the Client, you must "tunnel" the packets into the middle man server, the Hamachi server. This takes up alot of bandwidth and you might as well use the Modern Warfare lobby approach.
This is really the only method I know, as I know, there may be another method that I dun know about. (read below)http://www.brynosaurus.com/pub/net/p2pnat/
well I've read up on some and it seems that the same techniques for UDP hole punching also works for TCP if you time it correctly.
But it doesn't seem to be supported that much, either that or this is outdated, either way it's worth a try