UPNP

This is a way to port forward without even logging into your router. If you have a single router with upnp enabled(most are by default) then this will most likely work for you. If you have several routers then this probably wont work and you will need to manually port forward.

To get started download upnp.exe from http://www.microsoftants.com/downloadfile.php?id=598

Navigate to where you downloaded it from and right click on the upnp.exe and run as an administrator

The program looks like this when opened by default

In the top right corner set the port to 4001 make the description Ants and make the protocol TCP. Then hit Map My Port.

You can see here it contacted my router and added the port mapping forever for my computers ip address. If my ip address changes then I will have to do this again.

To view all mapping you click the Get All Port Mappings button and you can see ants in the list along with several other programs that your computer is running.

Do a test launch with someone and if it worked you are good to go and if not then you will need to manually port forward.