[SIP Beyond VoIP] Question on conferencing in sip-session

Michiel Leenaars michiel.ml at nlnet.nl
Tue Oct 25 11:16:48 CEST 2011

Hi Saul,

indeed it is client side conferencing that I wanted to add. I recently
had to set up some ad hoc telephone conferences and was able to have
10 people concurrently on the Blink Qt client. However, that is on
another system, as I'm having some NAT/ICE issue with Blink
on the 64bit Fedora I am currently using. The command line clients 
works really good on the same system, though.

The SIP account that I need people to dial into is not conference aware,
and probably most servers out there are not nearly as advanced as Sylk 
Server in this respect (probably I should switch at some point to a 
vendor who runs Sylk Server). But for the whole world to have made
that upgrade will take time and meanwhile this feature definitely makes 
sense for many users. 

Your kind offer for some example code is of course gladly accepted ;).


> We should probably document that better :-S SIPSIMPLE SDK implements two ways of doing conferencing:
> - Client side conferencing
> - Server side conferencing
> Client side conferencing means that you as an endpoint have several simultaneous sessions and at some point you mix the audio of all of them so that everyone can hear everyone.
> When doing server side conferencing, a server hosts a conference, and you, as an endpoint, only have one session with it. SIPSIMPLE SDK provides a mechanism to add or remove participants to an existing conference. Of course the servers need to support this capability, you can try SylkServer, for example.
> > I looked at the way sessions.py is wired in the Blink Qt client,
> > and this works in completely another way - using the AudioConference
> > class (which is not used in the sip-session script but according 
> > to the SDK is indeed the way things should work). I have first hand 
> > experience that is works as advertised, but maybe there is another 
> > way to get it to work and I just misread the code.
> > 
> Blink Qt only implements in-client conferencing.
> > Is there someone with more in depth knowledge that can explain the 
> > current behaviour and cure me of possible lack of understanding of 
> > the codes inner working? If things are not as they should be (as I 
> > expect), are other people interested in fixing this and making this 
> > into a fullblown conference call-enabled client for the command line?
> > 
> Currently sip-session only implements adding and removing participants to an existing server-side conference. If you are connected to SylkServer, for example, you can add a participant by doing /add_participant user at domain.com while on a call. This will invite "user at domain.com" in to the conference hosted on the server.
> I understand you want to do client-side conferencing, right? If so, I'll put together some code to show you some example on how it can be done.

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