How to port forward automatically in java?

Question

I know that bit torrent clients use automatic port forwarding (Port forwarding with having to configure the router) so that they can connect to each other. I want the users in my application to be able to host a server without having to configure the router. So I was wondering how you would do so in java?

Answer 1

You can use UPnP (Universal Plug and Play) port forwarding. One library mentioned is Cling, but there's much simpler library - WaifUPnP, which allows you to forward a port with just one line like:

UPnP.openTCP(portnumber);

Answer 2

UPnP is your friend. It is a standardized method which allows automatically configuring routers to forward ports. There are a couple of different ways to do it. One package that supports UPnP under Java is Cling. http://4thline.org/projects/cling/