Andrej, there are number of ports (channels in common language) from which only one is responsible for data reception-transmittion. All these ports have numbers (like we have names) to identify them uniquley. Some of these ports are busy. There are some proceess we cant see but they are using some of these ports for their receining-transmision process. BitComet also wants you to choose one of these port for its data traffic. We cant say which one would be free from traffic, so we have to cross fingers and choose randomly.
Hope I was able to make you understand your point. I am a computer engineer and cant wait to share knowledge if I know it.
