[event handler] onreceived [event type] MessagingEvent [short description] handles received messages [event name] 
received
r e c e i v e d
s e n t
d e l i v e r y s u c c e s s
d e l i v e r y e r r o r
s e r v i c e a d d e d
s e r v i c e r e m o v e d