Re: new wifi connection = nntp timeout = Emacs restart?

[David Engster <deng@randomsample.de>]

> Hey, that's pretty handy! Just FYI, the function name is quoted
> unnecessarily

Oops...

> and sleep-start is actually nil when it's going to sleep,
> who knows why.

Uhm, not for me. I just tested again to make sure. On sleep it is 't',
on wakup it is nil. This is also the documented behavior:

  The PrepareForShutdown() resp. PrepareForSleep() signals are sent right
  before (with the argument True) and after (with the argument False) the
  system goes down for reboot/poweroff, resp. suspend/hibernate.

https://www.freedesktop.org/wiki/Software/systemd/logind/

> Particularly handy since, in all my years of using dbus machines, I have
> never managed to write a dbus rule that did anything other than fail
> silently. This is useful.

You can actually do pretty nifty things with DBus, but it's... well,
let's say: convoluted. But Michael Albinus has really done a great job
for the Emacs interface, it's really simple to use and well documented.

As for detecting networking changes, I don't think it is possible to do
this with the systemd networking.service only, you'll also need
NetworkManager. I tried NetworkManager years ago and it was... really
not good. I just tried it again today and was happily surprised how well
it works nowadays. Some things just need time.

So NetworkManager will tell you everything you need to know via DBus:

https://developer.gnome.org/NetworkManager/stable/gdbus-org.freedesktop.NetworkManager.html

So from that I guess checking for changes on 'State' makes the most
sense?

(defun my-network-state-handler (name change-vals change-novals)
  (let ((state (assoc "State" change-vals)))
    (when state
      (message "New State: %s" (caadr state)))))

(dbus-register-signal :system
		      "org.freedesktop.Networkmanager"
		      "/org/freedesktop/NetworkManager"
		      "org.freedesktop.DBus.Properties"		      
		      "PropertiesChanged"
		      'my-network-state-handler)

So if you evaluate this and put your network down, you should see
something like

New State: 30
New State: 20

And if you put it up again:

New State: 40
New State: 50
New State: 60
New State: 70

The numbers are explained here:

https://developer.gnome.org/NetworkManager/stable/nm-dbus-types.html#NMState

So from that I guess we should just call gnus-close-all-servers for
state=30:

  Network connections are being cleaned up. The applications should tear
  down their network sessions.

-David