Not sending Keep Alive packets to sip server

What steps will reproduce the problem?
1.Register our client 
2.Intiate call to other sip client
3.Call accepted by other client 

What is the expected output? What do you see instead?
Keep alive packets is not sending to sip server.

What version of the product are you using? On what operating system?
iOS 5.

Please provide any additional information below.
Keep alive packets must be sent to sip server to keep connection alive, other 
wise sip server will close port after 4 minutes. Other wise there will be not 
message after that. MEssages like bye etc.

Original issue reported on code.google.com by gaurav.v...@gmail.com on 20 Jun 2012 at 5:55

barchandune / doubango

Not sending Keep Alive packets to sip server #122