code: public void processEvent(EventObject event) {
      // Don't need to do anything except resend if challenged
      // (we only get here for a stateless NOTIFY)
  
      if (event instanceof ResponseEvent) {
        receivedResponses.add(new SipResponse((ResponseEvent) event));
        resendWithAuthorization((ResponseEvent) event);
      }
    }
docs: /*
  @see org.cafesip.sipunit.RequestListener#processEvent(java.util.EventObject)