goto command prompt

Windows
netstat -aon

for linux
netstat -tulpn | grep 'your_port_number'
it will show you something like

 TCP    192.1.200.48:2053      24.43.246.60:443       ESTABLISHED     248
 TCP    192.1.200.48:2055      24.43.246.60:443       ESTABLISHED     248
 TCP    192.1.200.48:2126      213.146.189.201:12350  ESTABLISHED     1308
 TCP    192.1.200.48:3918      192.1.200.2:8073       ESTABLISHED     1504
 TCP    192.1.200.48:3975      192.1.200.11:49892     TIME_WAIT       0
 TCP    192.1.200.48:3976      192.1.200.11:49892     TIME_WAIT       0
 TCP    192.1.200.48:4039      209.85.153.100:80      ESTABLISHED     248
 TCP    192.1.200.48:8080      209.85.153.100:80      ESTABLISHED     248
check which process has binded your port. here in above example its 248 now if you are sure that you need to kill that process fire

Linux:
kill -9 248

Windows:
taskkill /f /pid 248

it will kill that process