How do I see if a port is in use on a windows machine?
Solution 1:
netstat -a -b will show all listening ports and the executable name (rather than just the PID).
If you prefer a graphical version, Microsoft's TCPView will show you the same information, updating in real-time.
Solution 2:
TCPview from the Sysinternals Suite does it in a nice, GUI way.
It includes a configurable update interval, address resolving and difference highlighting. And it is a lot faster than netstat -a -b.
Also available as a command line version (tcpvcon.exe). Both are free.