How to use "connect" command?

[Augusto Oliveira]

Hello, I need help connecting a new participant to a call.

I have an established call between two phones (callId A) through RTPEngine and would like to add a new participant without going through an offer/answer renegotiation.

I noticed that RTPEngine has a "connect" command that could solve this, but I couldn't quite understand how it works.

To test it, I made a "fake" call between the third participant and a NodeJS server (callId B) through RTPEngine and then used the "connect" command using the following properties:

"call-id" - "A"
"from-tag" - containing the tag of one of the participants in callId "A"
"to-tag" - containing the tag of the new participant I want to add
"to-call-id" - "B"

Well, the "connect" command was successfully interpreted and responded to by RTPEngine, but there was no audio between the from-tag and to-tag participants.

I've had other trouble with rtpengine before and always ended up being wrong, so this time shouldn't be any different. Any ideas on how to get this working?

[Richard Fuchs]

On 22/08/2025 20.17, Augusto Oliveira wrote:
> Hello, I need help connecting a new participant to a call.
>
> I have an established call between two phones (callId A) through
> RTPEngine and would like to add a new participant without going
> through an offer/answer renegotiation.
>
> I noticed that RTPEngine has a "connect" command that could solve
> this, but I couldn't quite understand how it works.
>
> To test it, I made a "fake" call between the third participant and a
> NodeJS server (callId B) through RTPEngine and then used the "connect"
> command using the following properties:
>
> "call-id" - "A"
> "from-tag" - containing the tag of one of the participants in callId "A"
> "to-tag" - containing the tag of the new participant I want to add
> "to-call-id" - "B"
>
> Well, the "connect" command was successfully interpreted and responded
> to by RTPEngine, but there was no audio between the from-tag and
> to-tag participants.

Based on your description, it sounds like you're doing it right. Do note
that the `to-tag` in the message might need to be set to the `from-tag`
from the offer/answer of your call B.

It's a fairly new feature and not well tested, so of course there's
possibility of something not working right. When in doubt, pull a full
debug log.

I'm a bit confused about your notion of "adding a participant" though.
The "connect" method doesn't establish a conferencing scenario or
anything like that. If an existing call is between A and B, and then
another call between C and D, telling rtpengine to "connect" A to C
would leave B and D without media. Hope that part is clear.

Cheers