At the Very Core
[Core SIP Library]

The very core of PJSIP.

Modules
	Endpoint
	The master, owner of all objects.
	Event
	Representation of events as they are distributed among modules.
	Modules
	Modules are the primary means to extend PJSIP! Modules are the primary means to extend PJSIP. Without modules, PJSIP would not know how to handle messages, and will simply discard all incoming messages.
	Target URI Management
	Management of target URI's in case of redirection This module provides utility functions to manage target set for UAC. The target set is provided as pjsip_target_set structure. Initially, the target set for UAC contains only one target, that is the target of the initial request. When 3xx/redirection class response is received, the UAC can use the functionality of this module to add the URI's listed in the Contact header(s) in the response to the target set, and retry sending the request to the next destination/target. The UAC may retry this sequentially until one of the target answers with succesful/2xx response, or one target returns global error/6xx response, or all targets are exhausted.
	Message Creation and Stateless Operations
	Utilities to create various messages and base function to send messages.