[pjsip] How to Know Offline Call

Joegen E. Baclor joegen.baclor at gmail.com
Sun Jan 17 22:23:58 CST 2010

If the server supports configurable redirects when a user is off-line, 
then you may register with the server as the redirect recipient.  This 
way, you will get a handle on the calls that are coming in for a 
particular off-line ua.  You can simply either reject the call with a 
4xx or play media acting as an announcement server.  Your next 
requirement would be to check whether the server supports reg-event 
package (RFC 3680).  If it does, then you can simply send a subscribe to 
the registration event of a particular ua to get notified when the ua 
goes back on-line.  The rest may be accomplished via proprietary MESSAGE 
or unsolicited NOTIFY exchange to notify the user of the missed calls 
while it is off-line.

IMHO, MWI is still the best standard approach to indicate to the user 
that it missed some calls while off-line.


Angelica Grace Tanchico wrote:
> Hello,
> I am planning to include notification/alert when an offline client 
> receives a call.
> I think this is useful like when a client was disconnected (or the 
> client application
> is just not running) and somebody tries to call him, receiving a 
> notification right
> after the client became online again (or the client app restarted and 
> running ok),
> I think is a nice feature.
> I am having difficult time figuring out how to do this since I don't 
> have control with
> the SIP servers the clients register to. I would like to hear some 
> useful inputs on
> how I can include tis feature.
> Thanks in advance!
> Regards,
> Gie
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