Find PID associated to port (Windows)

// in cmd
netstat -aon | find "PORT_NUM"

// In bash:
netstat -na | grep "8080"

// In PowerShell:
netstat -na | Select-String "8080"

Sample Output:
  TCP    0.0.0.0:4848           0.0.0.0:0              LISTENING       9856
  TCP    [::]:4848              [::]:0                 LISTENING       9856

taskkill /F /PID 9856

Anyway you can stop the process which uses your port and let your application take it.
Use netstat -a -o -n to check for the port usages.
Use taskkill /F /PID <pid> to kill that process.