Calibre-server ubuntu server

I have started calibre-server through the command line calibre-server --daemonize on ubuntu server.

Now that I want to stop the process, there is two process, one that I can cancel and another one that is in stat s+ and change pid so I can't cancel.

The second process seems to me a listener. Is there a formal way to stop calibre-server from running when launch by the command line ?

Thanks!