1. Open command line (CMD)

  2. Type netstat -aon | findstr "[port_number]". Replace the [port_number] with the actual port number that you want to check and hit enter.

  3. If any application uses the port, then that application's detail will be shown. The number, which is shown at the last column of the list, is the PID  (process ID) of that application.

  4. Type tasklist | findstr "[PID]". Replace the [PID] with the number from the above step and hit enter.

  5. You'll be shown the application name that is using your port number.