Establish
1) A->B, Syn message include sequence number X
2) B->A, Ack with X+1 and Syn with sequence number Y
3) A-> Ack with Y+1
Finsih
1) A-> B FIN Seq=K +ACK (seq=L)
2) B-> A ACK (seq=K+1)
3) B->A Fin (Seq =L), ACK=K+1
4) A->B ACK = L+1
Establish
1) A->B, Syn message include sequence number X
2) B->A, Ack with X+1 and Syn with sequence number Y
3) A-> Ack with Y+1
Finsih
1) A-> B FIN Seq=K +ACK (seq=L)
2) B-> A ACK (seq=K+1)
3) B->A Fin (Seq =L), ACK=K+1
4) A->B ACK = L+1
原文：https://www.cnblogs.com/anyu686/p/8655265.html