UT2004 Server Ports

Incoming:
7777-7778 UDP
7787-7788 UDP
28902 TCP
{Webmin Port TCP}

Outgoing:
27900 UDP
28902 TCP/UDP

Obviously, set the webmin port as specified in your UT2004 configuration.

If using the non-default port 7777, simply change the incoming ports:
Port+0 / Port+1 UDP
Port+10 / Port+11 UDP
28902 TCP
{Webmin Port TCP}