Kill process in shell

1. Check for Zombie Processes

Use the ps command to check for zombie processes.

ps aux | grep 'Z'

Use lsof or netstat to check if the port is still being used and by which process

sudo lsof -i :60001

This is show all of 60001 ports processes, you can check the PID in there.

kill [PID] kill -9 [PID]

This means force to stop process

The problem I met is my computer always had two processes, one from Java, one from sudo. So I need to kill the sudo, because cooja run in Java.