I cant tell you how to open ports for your particular router. You should check out the documentation or the routers web site for that info.
I can point you to my site,
http://www.mohadmin.com for a complete list of ports needed to run MOH:x.
It's more then just one.
once at MOHadmin.com follow the link on the left to the guides section. Your looking for Dogmeat's port guide.
good luck