Wait for SMS messages

[Dan Williams]

On Fri, 2025-01-31 at 09:27 -0600, Dan Williams wrote:
> On Thu, 2025-01-30 at 23:46 +0000, Brendan Simon wrote:
> > 
> > IND.T Classification: Public
> > 
> > 
> > 
> > 
> > From: Dan Williams <dan at ioncontrol.co>
> > 
> > 
> > 
> > Sent: Thursday, 30 January 2025 3:39 AM
> > 
> > On Tue, 2025-01-28 at 12:05 +0000, Brendan Simon wrote:
> > > 
> > > What's the best way to monitor and wait for SMS messages for
> > > processing?
> > > I'm using a Debian based system and python3.
> > > I was thinking of something involving systemd and/or a python
> > > package
> > > such asdbus_next.
> > 
> > With Python we'd typically use the bundled GObject introspection
> > data
> > to directly work with libmm-glib. There are some examples in MM
> > git:
> > 
> > https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/tree/main/examples?ref_type=heads
> > 
> > I added an SMS watcher example here:
> > 
> > https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/1284
> > 
> > Hopefully that's easy enough to follow, all questions welcome.
> > 
> > It does require a bit of D-Bus knowledge to fully understand the
> > flow,
> > but even without that you just plug your own code into the
> > SmsWatcher's
> > show() method and that'll run for any "new" SMS from any modem. I
> > say
> > "new" in quotes because it'll also print out any messages in the
> > modem
> > at the time it's run, then wait for new ones from the network or
> > local
> > addition.
> > 
> > 
> > I tried the SMS watcher example.
> > It seems to work mostly, however in the code snippet below, the new
> > message does not appear in the list from list_sysnc(), and
> > therefore
> > the sms object is never added to self.messages.
> > Is this expected or is there something else missing?
> 
> Are you able to post the ModemManager-side --debug output of
> receiving
> the message?
> 
> I did test the code out (QMI-based Huawei LTE device) and it works
> here, but that doesn't at all mean you're wrong about it failing for
> you.
> 
> > What is the purpose of SmsWatcher?  Why do I need to "watch" SMS
> > messages once we have processed them with MessagingWatcher?
> 
> It's for multi-part messages, where the parts are received at
> different
> times and are technically different SMS messages, but really a single
> big SMS.
> 
> When MM sees a piece of a multipart message, it'll create the SMS
> object to track all the pieces and then change the SMS's 'State'
> property to indicate when all parts have been received.
> 
> The partial SMS still needs to be exposed to clients somehow just in
> case it never becomes complete, since the message can still take up
> storage.
> 
> That all said, we could perhaps make clients easier to write by
> adding
> convenience methods so you don't have to watch the SMS objects
> themselves as much. It's also silly that we have to list all SMS
> again
> just to get the one we want.
> 
> > Is it for things like handling message deletion or other events?
> > 
> > 
> > ```python
> >     def on_sms_added(self, messaging, path, received):
> >         for sms in self.iface.list_sync():
> >             if sms.get_path() == path:
> >                 #>>> NEVER GETS HERE AS THE NEW MESSAGE DOES NOT
> > APPEAR IN THE RETURNED LIST OF MESSAGES !!!
> 
> Yeah, this seems like an issue; any SMS for which the "Added" signal
> is
> sent by definition should be in the explicitly requested SMS list.
> The
> ModemManager --debug output may be able to help with that.
> 
> The other thing you should do is run:
> 
> sudo dbus-monitor --system
> "type='signal',sender='org.freedesktop.ModemManager'"

One small mistake here: that should be 'org.freedesktop.ModemManager1'
eg with a '1' at the end.

Dan

> 
> before sendind the new SMS and include that output along with the MM
> debug output (remove private info like phone numbers of course!).
> That
> shows us exactly what MM is doing, as opposed to what the client side
> (sms-watch-python) is doing and can help us narrow down the issue.
> 
> Thanks,
> Dan
> 
> >                 # Watch this SMS
> >                 self.messages[sms.get_path()] = SmsWatcher(sms)
> > ```
> > 
> > 
> 
> 
>