[asterisk-app-dev] Debugging ARI apps and mixing bridge with DTMF events

[Nick Horelik]

Hello,

I've been using ARI for a few months to build some basic apps with some
success - I definitely like the interface!

Lately I've run into an issue that I'm not sure how to solve, and I wanted
to ask about best ways to debug.  I'm still a little new to Asterisk in
general, so I apologize in advance if I'm missing something simple.

Right now I'm trying to build a simple app to test the registration of DTMF
events over a specific trunk that doesn't use rfc4733 for dtmf_mode - they
only support rfc2833 and sip-info.  I figured out by looking at the source
of res/res_pjsip/pjsip_configuration.c that I can set dmtf_mode=info on my
endpoint in pjsip.conf (I had trouble finding documentation on this - is
there somewhere I can look for more info about dtmf_mode?), so I'm hoping
that this will work for me.  I didn't see the option to use rfc2833 with
pjsip.

The testing app flow is very similar to some of the ari-py examples, and
goes like this:

1 - Run the app using ari-py
2 - Originate a call to my cell phone over a trunk that I know works with
the default dtmf_mode, and send to the app:
client.channels.originate(app='appname',appArgs='incoming',endpoint='PJSIP/<cellphone_1>@<working_dtmf_trunk>')
3 - In on_start in the app for the 'incoming' channel, put the channel into
a bridge created with:
client.bridges.create(type='mixing,dtmf_events')
and then originate a channel to another phone using the other trunk set up
with a different dtmf_mode:
client.channels.originate(app='appname',appArgs='outgoing',endpoint='PJSIP/<cellphone_2>@<bad_dtmf_trunk>')
4 - In on_start in the app for the 'outgoing' channel I add the channel to
the same mixing bridge, and register a function to the ChannelDtmfReceived
event

Everything works fine if I send the 'outgoing' channel over
<working_dtmf_trunk>:  the cellphones are connected successfully (I can
hear audio from one to the other) and my function registered to
ChannelDtmfReceived successfully gets triggered when I press keys on
cellphone_2.  The cellphones are also successfully connected when using
<bad_dtmf_trunk> for the 'outgoing' channel, when I use a bridge created
with:

client.bridges.create(type='mixing')

Of course in this case the dtmf events are not captured.  Here's where I'm
stuck: when I use 'mixing,dtmf_events' for the bridge to connect the
'outgoing' channel over <bad_dtmf_trunk>, the phones do not seem to be
successfully connected.  The second cellphone rings and I can answer the
call, but I can't hear audio between the phones and my function registered
to ChannelDtmfReceived is never triggered.

Am I missing something fundamental with what I'm trying to do here?  I'm
happy to post my pjsip.conf if you think my issue might lie there.  If
everything looks good I can try working with support at this specific
trunk, but I want to make sure the issue isn't on my end before pursuing
that.

Separately from the specifics of this example, what's the right way to
debug these sorts of issues?  I've tried checking
/var/log/asterisk/messages, setting up logs with cel_custom.conf, watching
the CLI while I try to test - I haven't yet found the right way to get any
more visibility into why it's not working.  At this point I'm considering
capturing packets to investigate it, but I feel like there must be a better
way. Also, is there an easy way to dump to a log all events that flow
through an ARI application, and not just ones I've registered functions to
in the app itself?

I am using Asterisk 12.6.0 compiled from source.  I would greatly
appreciate any tips - thank you so much in advance.

Best,

Nick
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