Are you referring to this setting in Preferences ==> Advanced ==> Tweaks?
Code:
#: What interfaces should the content server listen on
# ID: server_listen_on
# By default, the calibre content server listens on '0.0.0.0' which means that it
# accepts IPv4 connections on all interfaces. You can change this to, for
# example, '127.0.0.1' to only listen for connections from the local machine, or
# to '::' to listen to all incoming IPv6 and IPv4 connections (this may not
# work on all operating systems)
server_listen_on = '0.0.0.0'
Because calibre-server should automatically use the settings in Tweaks regardless of whether it runs via the GUI or the cli entry point.
Also, the default listens on every interface.