tcp retransmission

帝国队长 2015-03-05 03:47:06

客户端与服务器连接，时间久了不活动就会中断
用抓包工具试了一下
当客户端与服务器连接后， 20分钟没有任何通信
当客户端再发送信息时，则出现
tcp retransmission 几次，应该是发不通重发
然后再收到一个RST，ACk

请问什么情况会出现这个。是不是久了不发信息超时了
服务器那边还没有接收到客户端的退出信息，整个抓包过程也没有收到FIN
也就是说客户端单放报出网络错误，服务器那边认为客户端还在线。
求大神们解决一下。

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cyj528 2017-04-25

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我遇到了一样的问题，客户端和服务端在手，两边抓包，从客户端上看发现客户端和服务端长时间保持连接但是没有数据交互。再次操作客户端时，tcp retransmission 几次，然后再收到一个RST，ACk。看服务端，服务端首先收到RST数据包，连接断开，但是这个数据包不是真正的客户端发出的。百度IP，发现客户端真实的外网IP就是发出RST数据包的机器，这台机器属于运营商路由器。

阿先森 2015-04-19

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感谢邀请。应该防火墙或者网络节点上的策略问题。

kuba120 2015-03-30

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在长连接下，有可能很长一段时间都没有数据往来。理论上说，这个连接是一直保持连接的，但是实际情况中，如果中间节点出现什么故障是难以知道的。更要命的是，有的节点（防火墙）会自动把一定时间之内没有数据交互的连接给断掉。在这个时候，就需要我们的心跳包了，用于维持长连接，保活加心跳包吧，你那个程序估计是长期无通信被什么节点的防火墙给断了

Sandrer 2015-03-06

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给套接字设置 SO_KEEPALIVE 试试

worldy 2015-03-05

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是否服务器发了心跳包，而客户端没响应而关闭了连接？使用原来的端口，重新打开socket试试，看是否能打开，如果能，说明原来的连接已经被关闭

帝国队长 2015-03-05

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双方都没有开防火墙。应该是和这个无关，而且这个必须等一段时间才会出来，如果正常连续发包，几天都不会有问题

oyljerry 2015-03-05

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会不会是防火墙block

帝国队长 2015-03-05

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返回错误是10053 10054 但问题是服务器什么都没有收到，信号都没有收到通过抓包工具来看，确实应该是命令都没有发过去，直接进入重发tcp retransmission了然后重发失败RST，ACk

lougd 2015-03-05

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客户端发送的时候api返回错误了吗？这个应该tcp retransmission应该是tcp协议层实现的吧，对用户层api是透明的吧。

因为tcp协议时三次握手的，所以tcp协议的通信链接时间会很长，尤其是当服务器ip和port不正确的时候，tcp链接的过程很费时间，如何处理链接超时问题就显得很重要了，这个文档就是如何处理该问题的代码。希望对需要的同学有帮助。

C++ TCP客户端非阻塞连接超时测试源码，主要用来简单测试非阻塞连接超时的，防止服务端未存在，超时重发（TCP Retransmission）卡住在那边

Our objective in this manuscript, is to address TCP’s Incast problem by providing transport layer solutions that are both practical and backward compatible. We approach this goal in two steps. First, we derive an analytical model of TCP Incast. Such a model is essential to understand the reasons behind TCP’s throughput collapse. The analytical model provides a closed form equation, which can be used to compute throughput at the client for various synchronized workloads. We verify the accuracy of our model against measurements taken from ns-2 simulations. Next, we discuss some solutions that were designed to address TCP Incast at the transport layer. Specifically, we develop transport layer solutions that improve TCP’s performance under Incast traffic, by either proactively detecting network congestion through probabilistic retransmission or by dynamically resizing TCP’s segments in order to avoid incurring timeout penalty. We evaluate the merits of the aforementioned solutions using ns-2 simulations. Results show that each of our suggested techniques outperforms standard TCP under various experimental conditions.

TCP/IP Illustrated, Volume 1: The Protocols W. Richard Stevens Publisher: Addison Wesley First Edition December 15, 1993 ISBN: 0201633469, 600 pages TCP/IP Illustrated, Volume 1 is a complete and detailed guide to the entire TCP/IP protocol suite - with an important difference from other books on the subject. Rather than just describing what the RFCs say the protocol suite should do, this unique book uses a popular diagnostic tool so you may actually watch the protocols in action. By forcing various conditions to occur - such as connection establishment, timeout and retransmission, and fragmentation - and then displaying the results, TCP/IP Illustrated gives you a much greater understanding of these concepts than words alone could provide. Whether you are new to TCP/IP or you have read other books on the subject, you will come away with an increased understanding of how and why TCP/IP works the way it does, as well as enhanced skill at developing aplications that run over TCP/IP.

TCP/IP Illustrated, Volume 1 is a complete and detailed guide to the entire TCP/IP protocol suite - with an important difference from other books on the subject. Rather than just describing what the RFCs say the protocol suite should do, this unique book uses a popular diagnostic tool so you may actually watch the protocols in action. By forcing various conditions to occur - such as connection establishment, timeout and retransmission, and fragmentation - and then displaying the results, TCP/IP Illustrated gives you a much greater understanding of these concepts than words alone could provide. Whether you are new to TCP/IP or you have read other books on the subject, you will come away with an increased understanding of how and why TCP/IP works the way it does, as well as enhanced skill at developing aplications that run over TCP/IP.

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