sudo netstat -lpn |grep :'3000'
3000 is port i was looking for, After first command you will have Process ID for that port
kill -9 1192
in my case 1192 was process Id of process running on 3000 PORT use -9 for Force kill the process
pkill is the easiest command line utility
pkill -f node
pkill -f nodejs
whatever name the process runs as for your os