Normally I'd be redirecting you to this page of our Wiki:
https://sourceforge.net/apps/mediawi...rewallsRouters
However since sourceforge.net has been shut off for 2 days now due to security problems, you will not be able to reach that page. As
Lord of the Rings already said, the default port that needs to be forwarded on TCP and UDP is 6346. However you can use the guides provided on portforward.com for correct manual setup. Also note that you need to configure your firewall, too (and in case you are using one different from the integrated Windows firewall, keep in mind you can only use one firewall simultaneously, so you will have to disable the Windows one in that case).