socket://Internet-IP:631 does not reach localhost:631

[NeroZero]

I am having a router that connects via DSl to the internet! On it is my PC where I run cups! Now I want my printer to be reached from the internet: i told my router to forward all TCP to internet-IP:631 to localhost:631! now why does it not work and the regular localhost:631 in the WWW browser does not appear. The attempt all but times out... Can it be that there is a configuration settings of cups that does not accept printing requests from out of the current subnet? How would I change this?