[asterisk-users] Channel names with semicolons

[Joshua C. Colp]

On Wed, Sep 7, 2022 at 11:17 AM Antony Stone <
Antony.Stone at asterisk.open.source.it> wrote:

> On Wednesday 07 September 2022 at 11:44:54, Antony Stone wrote:
>
> > Hi.
>
> This is a follow-up to an email I posted earlier today to the list,
> although I
> haven't seen it come back yet.  If it's under moderation for some reason,
> I
> hope some kindly admin will release it :)
>

There's nothing in the moderator queue that I can see.


>
> > I'm trying to deal with a problem regarding putting a call on hold and
> then
> > later resuming it.  I am using chan_sip throughout, and Asterisk 16.
>
> <snip detail from previous email>
>
> > The main thing which is puzzling me about this is that I see examples of
> > both Local/number at context-00000ce9;1 and Local/number at context-00000ce9;2
> > during the processing of the calls.
> >
> > What is the significance of the number following the semi-colon?
> >
> > I also see in verbose logging output:
> >
> > [2022-09-07 09:37:57.310706] pbx VERBOSE[29148]: dial.c:598 in
> > handle_frame: Local/number at context-00000ce9;1 answered
> >
> > [2022-09-07 09:37:57.310792] pbx VERBOSE[29155][C-00001265]:
> > bridge_channel.c:2252 in bridge_channel_internal_push_full: Channel
> > SIP/Trunkname-00002b55 joined 'simple_bridge' basic-bridge <7e260e93-
> > abd4-48ea-96f1-33601165dba2>
> >
> > [2022-09-07 09:37:57.310937] pbx VERBOSE[29149][C-00001265]:
> > bridge_channel.c:2252 in bridge_channel_internal_push_full: Channel
> > Local/number at context-00000ce9;2 joined 'simple_bridge' basic-bridge
> > <7e260e93- abd4-48ea-96f1-33601165dba2>
> >
> >
> > So, when the channel Local/number at context-00000ce9;1 gets answered, the
> > result is to bridge the channels Local/number at context-00000ce9;2 and
> > SIP/Trunkname-00002b55
>
> I see something very similar in the documentation about local channels at
>
> https://wiki.asterisk.org/wiki/display/AST/Using+Callfiles+and+Local+Channels
> -
> there are examples of both devices-ecf0;1 and devices-ecf0;2 but no
> mention of
> what the final digit means.
>
> Can anyone enlighten me please?
>

A single channel can't do two things at once (you can't have a channel
talking to Alice while also executing the Voicemail dialplan application
for example) - so Local channels solve this by having two independent
channels that exchange things back and forth internally. The ;2 leg is the
one that gets sent into the dialplan, while the ;1 leg is doing whatever
dialed it decides to do with it. If you send audio to ;1 it then pops out
of ;2, and vice versa.

-- 
Joshua C. Colp
Asterisk Project Lead
Sangoma Technologies
Check us out at www.sangoma.com and www.asterisk.org
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