Spring RTS Engine

ok for some reason when i try to host a game with me and my friend, i get the message:

"Warning : [my friend's name] doesn't support NAT Traversal"

idk what this even means
i THINK i opened my port correctly, but how can we get this to work?

your friend's (or you've) got a problem, probably a firewall or a very nazi ISP (university, perhaps?)

i need to know specifically what the problem is and how to fix it

Wikipedia wrote:The default behavior of Windows XP SP2 was changed to no longer have NAT-T enabled by default, because of a rare and controversial security issue.

sounds liek it is your friends computer. to really help we would need to know his network specs (system specs wouldnt hurt either).

I have my ports forwarded properly and I see this constantly in games I host. The players are usually still able to connect fine.