Kill a running process

If you know the port already:

$ kill -9 $(lsof -ti:<port>)
$ kill -9 $(lsof -ti:8080)

Finding the process

To find the process running on port:

# Find process id of a program running on port 3000
$ lsof -i tcp:3000

# Find process id of a program listening on port 8080
$ lsof -i :8080 | grep LISTEN

Finding the command running

# Find the command running on PID
$ ps -ef <PID>
$ ps -ef 42975

Kill the process

# Kill the process by PID
$ kill -9 <PID>

Using netstat

$ netstat -vanp tcp | grep 3000