I have 3 Skulltag servers (Doom2, Heretic, Hexen), 3 ZDaemon servers (same 3 games), & 1 Odamex (coz they only do doom) servers running.
Odamex uses port 10666.
Skulltag gets 10667, 10668, 10669.
ZDaemon gets 10670, 10671, 10672.
I port forwarded those ports on my NAT router.
I use IDE and can only see my Odamex server and none of the others.