If you're using a gateway router for Cable/DSL (such as from D-Link, Netgear, Linksys, et cetera) then you need to look at the port forwarding section for Linksys, or SUA servers for Netgear, and I don't know what other brands call it. Read the manuals or search to find out exactly what you need to do.
If you're not using a router and are using WinXP with the Internet Connection Firewall enabled, you'll need to read the instructions for that. If you're not using XP or you don't have the ICF enabled, then you don't have port 1227 blocked off in the first place.