请高手帮忙分析wireshark抓包出现的双向重传（一侧dup ack,双向都TCP Out-Of-Order）和发送包长度为 0 的问题，先谢谢

jimy1 2017-11-23 10:17:36

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

对端的抓包记录（截取了一段），TCP Out-Of-Order 在客户端也是每次发送都会出现，但多一个 TCP Dup ACK，TCP Dup ACK 大概每 15 个包会出现一次，先谢谢帮忙的各位：



	1	0.000000	10.254.251.74	10.254.251.103	TCP	9978 > 39934 [PSH, ACK] Seq=1 Ack=1 Win=817 Len=8 TSV=132194778 TSER=3044963545

	4	0.019092	10.254.251.103	10.254.251.74	TCP	39934 > 9978 [PSH, ACK] Seq=1 Ack=9 Win=115 Len=672 TSV=3044963566 TSER=132194778

	5	0.019111	10.254.251.103	10.254.251.74	TCP	[TCP Out-Of-Order] 39934 > 9978 [PSH, ACK] Seq=1 Ack=9 Win=115 Len=672 TSV=3044963566 TSER=132194778

	6	0.020369	10.254.251.74	10.254.251.103	TCP	9978 > 39934 [PSH, ACK] Seq=9 Ack=673 Win=817 Len=8 TSV=132194799 TSER=3044963566

	7	0.023970	10.254.251.103	10.254.251.74	TCP	39934 > 9978 [PSH, ACK] Seq=673 Ack=17 Win=115 Len=786 TSV=3044963571 TSER=132194799

	8	0.023976	10.254.251.103	10.254.251.74	TCP	[TCP Out-Of-Order] 39934 > 9978 [PSH, ACK] Seq=673 Ack=17 Win=115 Len=786 TSV=3044963571 TSER=132194799

	9	0.024614	10.254.251.74	10.254.251.103	TCP	9978 > 39934 [PSH, ACK] Seq=17 Ack=1459 Win=817 Len=8 TSV=132194803 TSER=3044963571

	10	0.027786	10.254.251.103	10.254.251.74	TCP	39934 > 9978 [PSH, ACK] Seq=1459 Ack=25 Win=115 Len=692 TSV=3044963575 TSER=132194803

	11	0.027791	10.254.251.103	10.254.251.74	TCP	[TCP Out-Of-Order] 39934 > 9978 [PSH, ACK] Seq=1459 Ack=25 Win=115 Len=692 TSV=3044963575 TSER=132194803

	12	0.028712	10.254.251.74	10.254.251.103	TCP	9978 > 39934 [PSH, ACK] Seq=25 Ack=2151 Win=817 Len=8 TSV=132194807 TSER=3044963575

	13	0.036293	10.254.251.103	10.254.251.74	TCP	39934 > 9978 [PSH, ACK] Seq=2151 Ack=33 Win=115 Len=843 TSV=3044963584 TSER=132194807

	14	0.036300	10.254.251.103	10.254.251.74	TCP	[TCP Out-Of-Order] 39934 > 9978 [PSH, ACK] Seq=2151 Ack=33 Win=115 Len=843 TSV=3044963584 TSER=132194807

	15	0.036581	10.254.251.74	10.254.251.103	TCP	9978 > 39934 [PSH, ACK] Seq=33 Ack=2994 Win=817 Len=8 TSV=132194815 TSER=3044963584

	16	0.040643	10.254.251.103	10.254.251.74	TCP	39934 > 9978 [PSH, ACK] Seq=2994 Ack=41 Win=115 Len=691 TSV=3044963588 TSER=132194815

	17	0.040651	10.254.251.103	10.254.251.74	TCP	[TCP Out-Of-Order] 39934 > 9978 [PSH, ACK] Seq=2994 Ack=41 Win=115 Len=691 TSV=3044963588 TSER=132194815

	18	0.041855	10.254.251.74	10.254.251.103	TCP	9978 > 39934 [PSH, ACK] Seq=41 Ack=3685 Win=817 Len=8 TSV=132194820 TSER=3044963588

	33	0.081157	10.254.251.103	10.254.251.74	TCP	39934 > 9978 [ACK] Seq=3685 Ack=49 Win=115 Len=0 TSV=3044963629 TSER=132194820

	34	0.081162	10.254.251.103	10.254.251.74	TCP	[TCP Dup ACK 33#1] 39934 > 9978 [ACK] Seq=3685 Ack=49 Win=115 Len=0 TSV=3044963629 TSER=132194820