Listening on a port?

Why does winscp open a port to listen to? It appears to be a random local port (i.e., launched twice, the port was different). Is this normal behavior? Why should it be?

WinSCP does not do that. You are probably mitaken by opened local port of outgoing connection. But it is not listening port. Any TCP/IP connection needs to have local port. Its number is assigned automatically by OS.