Step 1:
Open up cmd.exe (note: you may need to run it as an administrator, but this isn't always necessary), then run the below command:
netstat -ano | findstr :<PORT>
EX. netstat -ano | findstr :1717
The area circled in red shows the PID (process identifier). Locate the PID of the process that's using the port you want.
Step 2:
Next, run the following command:
taskkill /PID <PID> /F