In order to host a game you need to forward your ports!
TCP: 42007
UDP 55166
To do this (windows 7)
1) control panel
2) administrative tools
3) windows firewall with advanced security
4) Inbound rules
5) New rule (on the right hand side)
6) make a rule that allows TCP 42007 through (i did public, private and domain)
7) make a rule that allows UDP 55166 through (again, public, private and domain)
8) if you are using a router (which most likely are) you will have to get access to it using an IP address, usually something like 192.168.0.1. and you'll again have to allow the same TCP and UDP number through your router.
After that you should be able to host! Hopefully this helps!
