I have a half-decent network connection, and I'm trying to get my port open so I can host a server.

I've gone into my router's page and did everything from this list, except for the IP address thing since it wouldn't fit?

When I start a server it doesn't show up on the list and after a few seconds I get "Disconnected from Master Server"

Any idea what it might be? Any steps that weren't on that list?

You firewall might be blocking it.

Go to

-Start
-Control Panel
-Security Center
-Windows Firewall
-Click on the Exceptions tab
-Add Port

Name - AoS (For mine)
Port - 32887
And click UDP

OK.

Maybe this will help.