code: public void onInviteEvent(javax.sip.RequestEvent requestEvent,
  			ActivityContextInterface aci) {
  
  		final ServerTransaction serverTransaction = requestEvent
  				.getServerTransaction();
  
  		try {
  			// send "trying" response
  			Response response = messageFactory.createResponse(Response.TRYING,
  					requestEvent.getRequest());
  			serverTransaction.sendResponse(response);
  			// get local object
  			final SbbLocalObject sbbLocalObject = this.sbbContext
  					.getSbbLocalObject();
  			
  			// send 180
  			response = messageFactory.createResponse(Response.RINGING,
  					requestEvent.getRequest());
  			serverTransaction.sendResponse(response);
  
  			setFinalReplySent(false);
  			// set timer of 1 secs on the dialog aci to send 200 OK after that
  			timerFacility.setTimer(aci, null,
  					System.currentTimeMillis() + 1000L, getTimerOptions());			
  						
  		} catch (Exception e) {
  			getTracer().severe("failure while processing initial invite", e);
  		}
  	}
docs: Event handler method for the invite SIP message.
  
  @param requestEvent
  @param aci