everyone's "behind a router"
are you using a proxy? or is your address provided via NAT? is there a firewall in effect, if so, what type/OS? do you have control over the router in question, or does anyone you can talk to have access to it--if so, you'll need to ask them to port forward the following range of ports to your machine's IP:
7777 - 7779
i understand that unreal tournament does some dynamic port allocation for UDP uplinks, so to be safe, you might want to extend the range up to 7780 (or possibly higher), but use some type of packet filter to limit usage of that range of ports to the UT server only.
and also punch a hole through port 27900 on your firewall to allow for master server updates.
if it's a linux firewall, you can send your network admin here:
http://tsmservices.com/masq/detailform.php3?222
and, according to Epic's documentation, you'll also need to change the server name to the *public* IP of the router interface that you're connected to. not quite sure how this works from a technical standpoint, other than providing a fallthrough for players who want to try and manually connect to your server via the UT client's "Open Location..." command.
hope this helps. good luck!
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ps: i got all this information from
www.theadminpage.com