How to stop a Daemon Server in Rails?

If when you try to run
rails s
you get this kind of error
2012-11-19 08:37:53] WARN TCPServer Error: Address already in use - bind(2)
Exiting

so you have a Daemon server running in this case you can kill it using the following combo
$ lsof -wni tcp:3000
to get the list of processes running in background
$ kill -9 PID
to kill the process using it's PID