How to list all the discoverable Guix systems in my network?

[Rodrigo Morales <me@rodrigomorales.site>]

I have a system (A) running Guix SD whose /gnu/store I use as a
repository for applications that I commonly install in other Guix SD
systems.

In system (A), I usually use "guix publish" to make it visible to other
systems. Whenever I install Guix SD in other system (B), I need system
(A) to be discoverable, I usually do this by running the following
commands in system (A)

#+BEGIN_SRC sh
sudo guix publish -u rdrg -a -C 0
sudo cp /etc/guix/signing-key.pub /tmp/system-a.pub
rsync /tmp/system-a.pub "$user@$host:/tmp"
#+END_SRC

and the following commands in system (B)

#+BEGIN_SRC sh
sudo guix archive --authorize < /tmp/system-a.pub
sudo herd discover guix-daemon on
#+END_SRC

Sometimes system (A) needs is turned off, so it is not discverable by
system (B). Before running a command in system (B), I want to know
whether system (A) is available or not.

My question is: In system (B), how to list all Guix systems that are
publishing and would be used for downloading packages when needed?