Connection Failed - which ports do I open?

Hey guys

I've searched these forums, and the wilderness that is the Net, to find the answer to this problem. And I've found the answer, along with 25 other answers that all say different things.

What ports do I need to open on my router so that a buddy can join me to play co-op?

Now, I've opened 2300 to 2307, and used a port checker to confirm they're all WIDE open. I've allowed ARMA2 through my Windows 7 firewall. I've done the winsock flush thingy at the CMD prompt. I've even tried DMZ'ing my PC.

And my mate still gets "Connection Failed". Yet a different mate on a different PC/ISP joins fine.

What could we be doing wrong? Co-op is the only way to play ARMA2, and this is killing us...

And my mate still gets "Connection Failed". Yet a different mate on a different PC/ISP joins fine.

This means it is almost 100% certain that the problem is with your friend's PC. Can he join other multiplayer games elsewhere on the internet? I would suggest that he forwards the port on his firewall as well (probably 2302) and this should fix the problem.

I'm the mate. And yeah it bites.

I can connect to any other server. Also worth mentioning, GunSlinger just got a new router - worked perfectly with the old one - but the port settings were the same...

Does anybody have a definitive list of ports that we should open?

This means it is almost 100% certain that the problem is with your friend's PC.

I <3 you TechnoTerrorist - you were correct. It was the other guy's connection, and after forwarding ports 2300 through 2307, and disabling his firewall, he joined without a single hitch. You're a lifesaver, thank you so much!