If you try and host an Internet game with Starcraft, and people can't join, it may be one of two problems.
The reason may be that your firewall is blocking connections, or your NAT is blocking it. (Network Address Translation)
You must open UDP port 6112 inbound to your computer.
For example, in Cisco IOS:
access-list 102 permit udp any any eq 6112
ip nat inside source static udp 10.1.11.46 6112 126.96.36.199 6112 extendable