Peer-to-peer SIP call with Android SIP Stack?

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http://stackoverflow.com – I have been looking for a way to set up the Android SIP stack to be able to establish a SIP call between two devices on the same network, in an ad-hoc manner. i.e without REGISTERing to a SIP server. I have not been able to get this to work, as the SIP Demo includes server registration, and I cannot get it to make or receive a call without this step. I am not even sure if this is supposed to be possible. The little mention of this I have been able to find is conflicting (some say it can be done with a specific set up which they do not say what is, and some say the Android SIP API is not mean (HowTos)