Just bought a 4 pack of this game to play with my buddies and after over an hour of frustration and trying everything possible we still can't get in a game together.

1) I have forwarded port 1234 on my router, and tried a bunch of other ports as well
2) We've all disabled all firewalls and antivirus stuff in case that is causing a problem
3) We've tried using TUNGGLE to simulate a LAN environment

No matter what we try we get the same "Server unreachable; check address and port"

This is a real drag as the game is a LOT of fun playing single player, and looks like it would be even more fun to play with friends.

Any ideas?

Dunno, but in the meantime why not play with other people in one of the multiplayer Invasion servers. You and your friends can create a squad and play together using Esc>Online settings.

There's not need to use Tunngle. The host just need to tell them his IP to the clients who want to connect (from http://checkip.dyndns.com/ for example).
Can we assume that you forwarded your port correctly to your own LAN IP? It needs to be UDP but on most routers you can choose bother TCP and UDP which is fine as well.