Force NAT UPNP port forwarding

Question

I would like to forward ports automatically with my application, however UPNP is off by default, but Spotify was able to forward ports when even UPNP is disabled, same applies to uTorrent and others.

How do I force port forwarding, or Enable UPNP on rounter, forward port and disable it again?

Answer 1

Maybe these services use UDP hole punching.

See: Wikipedia article