Hi.

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.

I have two scenarios:

First (works):

1. An inbound call arrives, the dialplan does not Answer() it.

2. The dialplan performs a Dial() to an external number, and when that gets answered, Asterisk automatically bridges the two channels together. The Dial() command includes an F() parameter to call a subroutine when the call ends.

3. In this case I get channel names such as SIP/Trunkname-00002ab6 and SIP/Trunkname-00002ab7

4. I can then put those channels on hold using the ChannelRedirect() command.

5. I can later resume the conversation (join the channels back together) with the Bridge() command.

Second (doesn’t work):

1. An Originate command (AMI) is used to tell Asterisk to Dial() out to an external number, and the call gets answered.

2. The dialplan then Dial()s out to a second external number, and when that is answered, Asterisk automatically bridges the channels together. The second Dial() command also contains an F() parameter to call a subroutine when the call ends.

3. In this case I get channel names such as Local/number@context-00000ce9;2
for the first call and SIP/Trunkname-00002b52 for the second call.

4. When I then put those channels on hold using the ChannelRedirect() command, the calls are placed on hold, and then the F() parameter hangup handler is immediately called and the calls end.

The main thing which is puzzling me about this is that I see examples of both Local/number@context-00000ce9;1 and Local/number@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@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@context-00000ce9;2 joined ‘simple_bridge’ basic-bridge <7e260e93- abd4-48ea-96f1-33601165dba2>

So, when the channel Local/number@context-00000ce9;1 gets answered, the result is to bridge the channels Local/number@context-00000ce9;2 and SIP/Trunkname-00002b55

So, is Local/number@context-00000ce9;1 some sort of “controlling channel” and I should be using this as the parameter to the ChannelRedirect() command, or is Local/number@context-00000ce9;2 the “real channel” which is bridged to the other call, in which case why does the hangup handler get called when I use ChannelRedirect() on this?

Maybe I should only be using Local/number@context-00000ce9 with no semicolon suffix in the ChannelRedirect()?

Any advice / guidance / explanation / pointers to documentation welcome 🙂

Thanks,

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