SIP stands for (Session Initiation Protocol). It is a protocol that let applications easily set up outgoing and incoming voice calls, without having to manage sessions, transport-level communication, or audio record or playback directly.
##Important class of SIP and there function
SipAudioCall
Handle the audio call over the internet.
SipError
Define error code return during sip
SipManager
Provide API for the task, such as iniating SIP connection and provide access related services.
SipSession
Represents a SIP session that is associated with a SIP dialog or a standalone transaction not within a dialog
Here I create simple walkitalki application, with the help of https://developer.android.com/index.html tutorial.
here are the screenhots
