为啥我用tcpdump抓的包跟别人不一样，这是什么鬼

[flying_music]

自己写的socket例子，就是简单的建立连接，然后发送了一个消息，tcpdump抓到的包是这样的

#三次握手
15:08:16.001864 IP localhost.58230 > localhost.5555: Flags [S], seq 3665500164, win 14600, options [mss 1460,sackOK,TS val 2628198544 ecr 0,nop,wscale 7], length 0
15:08:16.001899 IP localhost.5555 > localhost.58230: Flags [S.], seq 2400661591, ack 3665500165, win 28960, options [mss 1460,sackOK,TS val 2974450587 ecr 2628198544,nop,wscale 7], length 0
15:08:16.002055 IP localhost.58230 > localhost.5555: Flags [.], ack 1, win 115, options [nop,nop,TS val 2628198544 ecr 2974450587], length 0
#发送数据
15:08:16.002130 IP localhost.5555 > localhost.58230: Flags [P.], seq 1:13, ack 1, win 227, options [nop,nop,TS val 2974450588 ecr 2628198544], length 12
#四次挥手
15:08:16.002152 IP localhost.5555 > localhost.58230: Flags [F.], seq 13, ack 1, win 227, options [nop,nop,TS val 2974450588 ecr 2628198544], length 0
15:08:16.002254 IP localhost.58230 > localhost.5555: Flags [.], ack 13, win 115, options [nop,nop,TS val 2628198544 ecr 2974450588], length 0
15:08:16.002346 IP localhost.58230 > localhost.5555: Flags [F.], seq 1, ack 14, win 115, options [nop,nop,TS val 2628198544 ecr 2974450588], length 0
15:08:16.002355 IP localhost.5555 > localhost.58230: Flags [.], ack 2, win 227, options [nop,nop,TS val 2974450588 ecr 2628198544], length 0

1. 为什么三次握手中，第三次ack就变成1了啊，不应该是3665500165+1吗？怎么搞的？
2. 发送数也没看到对应的ack啊，直接就挥手吗？