请高手帮忙分析 wireshark 抓包出现的单向重传和发送包长度为 0 的问题，先谢谢

[jimy1]

如下是拷贝的抓包描述，每次 10.254.251.74 发给 10.254.251.103 都会发 2 次然后才会有从 103 回包，wireshark 提示[TCP Out-Of-Order]（应该是因为 2 次的 seq 号一样导致）

还有一个问题就是隔几个包 10.254.251.103 会给 10.254.251.74 发送一次长度为 0 的包，然后才发送包含数据的报文。

10.254.251.103 是客户端，和 10.254.251.74 长连接发送业务数据，10.254.251.74 会存储收到的业务数据，10.254.251.74 收到业务数据后回“ 0004OK..”给 10.254.251.103 （如果回的时候 socket 写不成功，则会尝试重写 3 次，连接不断只重写）

850	0.297317	10.254.251.103	10.254.251.74	TCP	52633 > 9978 [PSH, ACK] Seq=1 Ack=1 Win=115 Len=693 TSV=1983788074 TSER=3365181331
857	0.299894	10.254.251.74	10.254.251.103	TCP	9978 > 52633 [PSH, ACK] Seq=1 Ack=694 Win=670 Len=8 TSV=3365181648 TSER=1983788074
858	0.299919	10.254.251.74	10.254.251.103	TCP	[TCP Out-Of-Order] 9978 > 52633 [PSH, ACK] Seq=1 Ack=694 Win=670 Len=8 TSV=3365181648 TSER=1983788074
859	0.300071	10.254.251.103	10.254.251.74	TCP	52633 > 9978 [ACK] Seq=694 Ack=9 Win=115 Len=0 TSV=1983788077 TSER=3365181648
868	0.303283	10.254.251.103	10.254.251.74	TCP	52633 > 9978 [PSH, ACK] Seq=694 Ack=9 Win=115 Len=689 TSV=1983788080 TSER=3365181648
871	0.303439	10.254.251.74	10.254.251.103	TCP	9978 > 52633 [PSH, ACK] Seq=9 Ack=1383 Win=670 Len=8 TSV=3365181651 TSER=1983788080
872	0.303441	10.254.251.74	10.254.251.103	TCP	[TCP Out-Of-Order] 9978 > 52633 [PSH, ACK] Seq=9 Ack=1383 Win=670 Len=8 TSV=3365181651 TSER=1983788080
873	0.305156	10.254.251.103	10.254.251.74	TCP	52633 > 9978 [PSH, ACK] Seq=1383 Ack=17 Win=115 Len=689 TSV=1983788082 TSER=3365181651
875	0.305851	10.254.251.74	10.254.251.103	TCP	9978 > 52633 [PSH, ACK] Seq=17 Ack=2072 Win=670 Len=8 TSV=3365181654 TSER=1983788082
876	0.305929	10.254.251.74	10.254.251.103	TCP	[TCP Out-Of-Order] 9978 > 52633 [PSH, ACK] Seq=17 Ack=2072 Win=670 Len=8 TSV=3365181654 TSER=1983788082
881	0.307979	10.254.251.103	10.254.251.74	TCP	52633 > 9978 [PSH, ACK] Seq=2072 Ack=25 Win=115 Len=748 TSV=1983788084 TSER=3365181654
888	0.309467	10.254.251.74	10.254.251.103	TCP	9978 > 52633 [PSH, ACK] Seq=25 Ack=2820 Win=670 Len=8 TSV=3365181657 TSER=1983788084
889	0.309472	10.254.251.74	10.254.251.103	TCP	[TCP Out-Of-Order] 9978 > 52633 [PSH, ACK] Seq=25 Ack=2820 Win=670 Len=8 TSV=3365181657 TSER=1983788084

[hcymk2]

TCP Dup ACK ?

[jimy1]

抓包文件打开后没有这个提示，只提示了 [TCP Out-Of-Order]

[jimy1]

up，同问追加提问时 是不是和提问一样的支持行首 tab 键是代码格式？