[pjsip] Handling connection drops on a mobile client

[Johan Lantz]

Hi

I have a general question on how to handle connection drops for a Mobile 
pjsip client, in this case Windows Mobile. In particular I would be very 
interested in which scenarios I can expect pjsip to resolve a connection 
reestablishment and where I have to take action myself.

In particular I am currently looking at what happens with my publish 
sessions if the connection is lost. One scenario is that the presence 
refresh timer is 300sec. I put the Windows Mobile phone into powersave 
by tapping the power button. Since wifi is used at this time the 
connection is instantly dropped. I then wait for more then 300 seconds 
which leads to the user presence beeing set to unknown in the server. 
When the connection is restored pjsip attempts to refresh the Publish 
but using the old e-tag value leading to the server sending a 412 in 
return. I assume this is because the server does not think the e-tag is 
valid anymore since the phone did not republish within 300 sec. As this 
happens my publish session is destroyed and I am not sure on the best 
approach to recover.

The questions:
1. For this specific case, do you think pjsip is doing this the right 
way or should a complete Publish be sent instead?

2. In general I am a unsure on how to handle connection drops and 
Publish failures. From my understanding the publish session is destroyed 
if a Publish fails. Is it completly up to the application to handle this 
scenario and do a complete republish when this occurs or do you have any 
guidelines for handling connection drops in general.

3. How does pjsip detect that a connection is again available. Is it on 
socket level or something else?

Sorry for beeing a bit vague I will try to get back with even more 
detailed scenarios when I understand what is my responsibility and what 
is handled by pjsip.

/Johan