1. Run command prompt.
2. Type netstat -ano | findstr 0.0:<port>
netstat -ano | findstr 0.0:80
The 8080 in the picture is the process ID (PID). You may see the corresponding application of the process ID through Windows Task Manager. You may also use another application such as XAMPP and run Netstat.
If there is no application using the port you provided, it will not return any value.