I have successfully forwarded these ports: 1200, 27000-27015, 27020-27039
I have disabled all antivirus software as well as the Windows firewall.
But my friend is still unable to join. He's tried connecting through friends, typing "connect xx.xxx.x.x" in console and he's tried looking in the server list but he couldn't find it.
I have tried typing in "sv_lan 0, sv_region 0, heartbeat 1" In console but he still cannot join.