I'm using Transmission right now.
The Transmission's test of the port says: port is closed. But there is seeding activity (around 160KB/s).
I re-checked the port with an online site. It says closed too. How is that possible??
I forgot to add that I use Ubuntu 12.04 and I enabled Upnp both in Transmission and in the router's interface.
Could seeding happen even if the port is closed?