Is there a way to force a direct connection?

Hi, I wish to play a game with a few friends, but all exept for one (who is nearly never online AND a teamkiller!) have relay connections. I was wondering if you could ‘force’ a direct connection?

I am an XP user, and most are xp users among us. The guy who can directly contact has windows 7 for sure.

We can sadly only play when he’s online.
All of us have steady and fast internet.

Thanks.

I am the same problem. Please help me