The server functions in this package will return server handles. You can pass the
handles to daemon_stop() to stop the daemonized servers.
daemon_stop(which = daemon_list())daemon_list()
the server handles returned by server functions; by default, all
existing handles in the current R session obtained from
daemon_list(), i.e., all daemon servers will be stopped by default
The function daemon_list() returns a list of existing server
handles, and daemon_stop() returns an invisible NULL.