3.1.5.1.3 Receiving a FIN Packet
When a FIN packet is received, the following applies:
If SMP is in the SESSION ESTABLISHED state, then move into the FIN RECEIVED state.
If SMP is in the FIN SENT state, then recycle the Session object and move into the CLOSED state.
When a FIN packet is received in the FIN RECEIVED state, an error SHOULD be raised to the higher layer and the underlying transport connection SHOULD be closed.
If the value of the SEQNUM field of the FIN packet is not equal to the value of the SeqNumForRecv variable of the Session object, an error MAY be raised to the higher layer and the underlying transport connection MAY be closed.