Thank you! I will try Csipsimple again out of curiosity.
I have a question tho.. You suggest "TCP keep alive" parameter to 1200 seconds i.e. 20 minutes.
It is time interval between subsequent SIP registrations, is not it?
Dows it mean that if within 20 mins you change network from wifi to data or vice-versa, you lose incoming calls and SMS for up to 20 mins
until next SIP registration?