From

https://www.printsupportcenter.com/hc/en-us/articles/115003386949-Determine-which-program-uses-or-blocks-a-port

Windows:

The Netstat.exe utility has a switch, that can display the process identifier (ID) that is associated with each connection to identify port conflicts. This information can be used to determine which process (program) listens on a given port.

Using Netstat command:

1. Open a CMD prompt
2. Type in the command: netstat -ano -p tcp
3. You’ll get an output similar to this one
4. Look-out for the TCP port in the Local Address list and note the corresponding PID number