ＳＯＣＫＥＴ端口问题

z32556601

我写的服务器端程序监听8089端口
通过tcpdump抓(ＨＴＴＰ)包发现一次连接,客户端为什么会用两个端口(４２０６９,４２０７０),而且是紧挨着的.

13:40:23.526549 IP localhost.42069 > localhost.8089: Flags [S], seq 2403824144, win 32792, options [mss 16396,sackOK,TS val 4065915 ecr 0,nop,wscale 4], length 0
13:40:23.526582 IP localhost.8089 > localhost.42069: Flags [S.], seq 4169872793, ack 2403824145, win 32768, options [mss 16396,sackOK,TS val 4065915 ecr 4065915,nop,wscale 4], length 0
13:40:23.526605 IP localhost.42069 > localhost.8089: Flags [.], ack 1, win 2050, options [nop,nop,TS val 4065915 ecr 4065915], length 0
13:40:23.527479 IP localhost.42069 > localhost.8089: Flags [P.], seq 1:401, ack 1, win 2050, options [nop,nop,TS val 4065915 ecr 4065915], length 400
13:40:23.527520 IP localhost.8089 > localhost.42069: Flags [.], ack 401, win 2048, options [nop,nop,TS val 4065915 ecr 4065915], length 0
13:40:23.528272 IP localhost.8089 > localhost.42069: Flags [F.], seq 1, ack 401, win 2048, options [nop,nop,TS val 4065915 ecr 4065915], length 0
13:40:23.528525 IP localhost.42070 > localhost.8089: Flags [S], seq 2836855418, win 32792, options [mss 16396,sackOK,TS val 4065915 ecr 0,nop,wscale 4], length 0
13:40:23.528549 IP localhost.8089 > localhost.42070: Flags [S.], seq 3932348166, ack 2836855419, win 32768, options [mss 16396,sackOK,TS val 4065915 ecr 4065915,nop,wscale 4], length 0
13:40:23.528566 IP localhost.42070 > localhost.8089: Flags [.], ack 1, win 2050, options [nop,nop,TS val 4065915 ecr 4065915], length 0
13:40:23.529179 IP localhost.42069 > localhost.8089: Flags [.], ack 2, win 2050, options [nop,nop,TS val 4065916 ecr 4065915], length 0
13:40:23.529745 IP localhost.42069 > localhost.8089: Flags [F.], seq 401, ack 2, win 2050, options [nop,nop,TS val 4065916 ecr 4065915], length 0
13:40:23.529796 IP localhost.8089 > localhost.42069: Flags [.], ack 402, win 2048, options [nop,nop,TS val 4065916 ecr 4065916], length 0
13:40:42.061317 IP localhost.42070 > localhost.8089: Flags [F.], seq 1, ack 1, win 2050, options [nop,nop,TS val 4070549 ecr 4065915], length 0
13:40:42.061359 IP localhost.8089 > localhost.42070: Flags [F.], seq 1, ack 2, win 2048, options [nop,nop,TS val 4070549 ecr 4070549], length 0
13:40:42.061368 IP localhost.42070 > localhost.8089: Flags [.], ack 2, win 2050, options [nop,nop,TS val 4070549 ecr 4070549], length 0