/// <summary>
/// Initialize pjsip stack
/// </summary>
/// <returns></returns>
public override int initialize()
{
// shutdown if started already
shutdown();
// register callbacks (delegates)
PjsipMethods.onDtmfDigitCallback(dtdel);
PjsipMethods.onMessageWaitingCallback(mwidel);
//PjsipMethods.onCallReplacedCallback(crepdel);
// init call proxy (callbacks)
pjsipCallProxy.initialize();
// Initialize pjsip...
int status = start();
// set initialized flag
IsInitialized = (status == 0) ? true : false;
return(status);
}