Initiator <- Responder : [e, ee, se], INFO..., HALT...
Initiator -> Responder : INFO..., FREQ..., DONE...
Initiator <- Responder : INFO..., FREQ..., DONE...
-Initiator -> Responder : FILE..., INFO..., DONE...
-Initiator <- Responder : FILE..., INFO..., DONE...
+Initiator -> Responder : FILE..., INFO..., DONE..., PING
+Initiator <- Responder : FILE..., INFO..., DONE..., PING
@enduml