Well, if you have linksys (router), then you should do this...
Open your Internet Browser.
Type in the address bar> 192.168.1.1
This will access your router, and then you'll put in your password which would be...something. lol,
For me its no login name needed, but just password. So, once you get your password, click on the Applications and Gaming, then enter in the port 6112 under "Start" and "End" fields. ((Don't forget the Application name "wc3" then select Both under "Protocol" then under IP Address put the number of your machine is. You can get that information from your local area connection computer thing at the bottom right side of your window. Right click that then "Status", then click "Support" and your IP number should be next to the "IP Address".
Other words you should see something like this in there
192.168.1.100
192.168.1.101
192.168.1.102
192.168.1.103
and so forth...which ever yours is then place that last three digit numbers in the "IP Address" field in the Linksystem under "Applications and Gaming". Once done
Check Enabled, then save settings. Enjoy!