我试图理解为什么客户端从服务器接收到第一个请求后没有关闭套接字/连接。客户端收到第一个报文后，仍然发送FIN报文。从tcpdump看来，SN和AN是正确的。
22:23:51.401992 IP 40.40.40.20.47542 > 1.1.9.20.http: Flags [S], seq 4194486305, win 29200, options [mss 1460,sackOK,TS val 177825438 ecr 0,nop,wscale 7], length 0
22:23:51.407176 IP 1.1.9.20.http > 40.40.40.20.47542: Flags [S.], seq 2103929166, ack 4194486306, win 28960, options [mss 1460,sackOK,TS val 172187280 ecr 177825438,nop,wscale 7], length 0
22:23:51.407214 IP 40.40.40.20.47542 > 1.1.9.20.http: Flags [.], ack 2103929167, win 229, options [nop,nop,TS val 177825439 ecr 172187280], length 0
22:23:51.407539 IP 40.40.40.20.47542 > 1.1.9.20.http: Flags [P.], seq 4194486306:4194486412, ack 2103929167, win 229, options [nop,nop,TS val 177825439 ecr 172187280], length 106
22:23:51.410830 IP 1.1.9.20.http > 40.40.40.20.47542: Flags [.], ack 4194486412, win 227, options [nop,nop,TS val 172187282 ecr 177825439], length 0
22:23:51.412266 IP 1.1.9.20.http > 40.40.40.20.47542: Flags [R.], seq 2103929167, ack 4194486412, win 0, length 0
22:23:52.963491 IP 40.40.40.20.47542 > 1.1.9.20.http: Flags [F.], seq 4194486412, ack 2103929167, win 229, options [nop,nop,TS val 177825828 ecr 172187282], length 0
22:23:53.367801 IP 40.40.40.20.47542 > 1.1.9.20.http: Flags [F.], seq 4194486412, ack 2103929167, win 229, options [nop,nop,TS val 177825930 ecr 172187282], length 0