I know it might sound stupid sorry but what is NAT port mapping, UPNP device, TCP and UDP ? And  also which range of listen port is the best for bitcomet? Before that, my download still ok around 30kb but now only around 2 to 7kb. I was wondering why. If tracker connection error, it is my connection? Is it my connection fault if NAT port mapping: Failed [UPNP device not found!]?