Android sip without SIP server

Question

I have been trying to develop an android sip client that connects through specifying the ip addresses of the devices involved.

Is it possible to make a peer-to-peer SIP call on android , without a SIP server registration ?

Answer 1

Though i could not do this using android APIs , Found an opensource which worked well on android phone. I was able to make a direct call within the local network, by specifying the IP of the other person.

http://www.linphone.org/eng/documentation/guide/

Answer 2

Yes! The SIP protocol does not prohibit peer-to-peer communications. In fact, the SIP protocol abstracts SIP Proxies and Registrars and does not define actual communication topology, outside of this implementation. In this scenario (peer-to-peer), you would not REGISTER any SIP UAC clients, instead each SIP UAC would implement it's own SIP Proxy (ie UAC+UAS, SIP Proxy listening on SIP ports). Client "A" would then simply send INVITE to Client "B" to initiate aa phone call.