网络协议详解TCP协议

haoayou · 发表于 2024-7-10 18:16:53

马上注册，结交更多好友，享用更多功能，让你轻松玩转社区。

您需要登录才可以下载或查看，没有账号？立即注册

×

<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">我相信有很多网友都看过《网络协议详解》的前5篇内容，看后大多数人的感觉是“有点儿偏理论知识！学会这些知识对实际工作没啥帮助！”<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">为了解决大家的这些困惑，我将实际项目遇到的问题结合理论知识给大家讲解，估计您看完这篇实战案例后就觉得的理论知识的重要性。这些理论知识可以真真正正的解决大家的实际问题。有的网友可能说“我的工作不需要这样的知识!”，而我想说的是“技不压身”，会的东西不是越多越好吗？<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">好了，言归到正题。这个案例可能有些网友在赵工的《我与PROFINET不得不说的事-08 案例分析》看到过，在这里我只想换个角度来说，我们的这个角度是：“如何将理论知识应用到实际的项目，并解决实际项目的问题”。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">这个案例涉及到了TCP协议的工作原理（感兴趣的可以在回顾看一下《网络协议详解03—TCP协议》），我们知道应用层的数据需要借助TCP传输层协议传输时，需要在通信的伙伴之间建立TCP的连接，这也是经常被称为“三次握手”，如下图所示：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505717672236991670600.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="377" height="385" src="/upload/image/20231114/1699959375556779.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">三次握手的过程中，标志位和序列号按如下图方式被设置：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505720052723543067416.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="363" src="/upload/image/20231114/1699959376989149.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">第一次握手：客户端发送标志位SYN=1, 发送序列号seq =x（这里x是客户端操作系统初始化的一个序列号）包到服务器，并进入SYN_SENT状态，等待服务器确认；<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">第二次握手：服务器收到SYN包，并会确认客户的SYN 请求，<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">服务器会发送一个标志位SYN=1 和ACK=1，确认序列号 ack=x+1（x是刚从客户端中接收到的发送序列号，通过x+1服务器确认收到了客户端SYN请求包），发送序列号 seq=y（这里y是服务器操作系统初始化的一个序列号）包到客户端，此时服务器进入SYN_RECV状态；<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">第三次握手：客户端收到服务器的SYN+ACK包，向服务器发送标志位ACK=1，发送序列号seq=x+1（x+1对于客户端来说已经发送过1个SYN的包，所以此次的序列号需要在初始的序列号x的基础上再加上1），确认序列号ack=y+1（y是刚从服务器端接收到的发送序列号，通过y+1客户端确认收到了服务器发来的 SYN+ACK的包）。此包发送完毕，客户端和服务器进入ESTABLISHED（TCP连接成功）状态，完成三次握手。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">可以看到握手时会在客户端和服务器之间传递一些TCP头信息，比如ACK标志、SYN标志以及挥手时的FIN标志等。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">除了以上这些常见的标志头信息，还有另外一些标志头信息，比如推标志PSH、复位标志RST等。其中复位标志RST的作用就是“复位相应的TCP连接”。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505724361892056635823.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="279" src="/upload/image/20231114/1699959377646254.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">导致“复位相应的TCP连接” 的其中一个原因是服务器端因为某种原因关闭了Connection，而客户端依然在读写数据，此时服务器会返回复位标志“RST”。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">RST复位标志发送原因几种可能：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">1. 被中间的防火墙设备拦截<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">2. 对方端口未打开<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">3. 全连接队列已满（超出了设备支持的TCP连接资源）<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">4. 设置 connect_timeout（应用设置了连接超时，sync 未完成时超时了，会发送rst终止连接。）<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">5. 非正常包（连接已经关闭，seq 不正确等）<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">6. TCP在建链时，发出SYN报文之后，60秒之内都没有收到对端的相应报文，会发送RST报文。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">7. TCP报文在连续重传阈值次数之后，都没有收到对端相应报文时，会发送RST报文。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">8. KeepAlive报文在连续发送5次之后，都没有收到对端的KeeAliveReply报文时，会发送RST报文。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">回顾完理论知识，我们在看一下现场的网络拓扑结构如下图所示：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505730076364194307143.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="309" src="/upload/image/20231114/1699959378169864.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">在华为的超融合网络中虚拟服务器中安装有MES系统和KEPServer OPC服务器。MES通过OPC的方式从KEPServer OPC 服务器读写数据，KEPServer OPC服务器通过自己集成的S7-300驱动程序经由路由的网络结构读写S7-1200和S7-1500中的数据（即KEPServer所在的虚拟主机在一个VLAN X子网，S7-1200和S7-1500在另一个VLAN Y子网）。KEPServer配置的驱动如下图所示：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505732855830418786025.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="451" height="370" src="/upload/image/20231114/1699959378487725.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505733589829236009591.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="449" height="372" src="/upload/image/20231114/1699959379312230.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">现场出现的问题是PLC采用 S7-1500+CP1543-1的方案通信没问题，即KEPServer OPC服务器可以正常读写PLC中的数据；但PLC采用S7-1200集成口或S7-1200+CP243-1 或 S7-1500集成口的方案时，KEPServer OPC服务器不能正常读写PLC中的数据。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">在现场已经排查出不是KEPServer OPC服务器的问题，在服务器所在的位置用TIA Portal 软件也无法在线连接到S7-1200。那现在只能怀疑超融合的网络可能有问题。为了验证，现场脱离了原有的超融合网络架构，用西门子SCALANCE XC208模拟超融合网络的路由网络架构。且IP子网设置与现场的超融合网络KEPServer OPC服务器所在虚拟主机相同的子网和相同的IP地址。模拟网络架构如下图：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505735900509293548862.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="518" src="/upload/image/20231114/1699959380174619.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">采用上面模拟的超融合网络架构的结果是所有的PLC都可以正常与KEPServer OPC服务器通信（S7-1200集成口、S7-1200+CP243-1、S7-1500集成口或S7-1500+CP543-1的方案都正常通信）。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">从测试的结果来看，不是PLC通信性能的问题，而是网络存在这一定的问题。为了找到问题的正真原因，我们在KEPServer OPC服务器所在的超融合网络的虚拟主机与S7-1200 PLC 上同时抓包分析(在PLC下载完程序启动的时候就开始抓包)。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505738478551385073916.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="312" src="/upload/image/20231114/1699959381730663.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">在KEPServer OPC 服务器端抓取到的文件命名为：“04_CP_1200_Fault_2023_10_28_CaptureInSERVER.pcapng”<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">在S7-1200 PLC端抓取到的文件命名为：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">“04_CP_1200_Fault_2023_10_28_CaptureInPLC.pcap”<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">KEPServer OPC 服务器所在的虚拟主机的IP地址“10.16.3.110“，子网掩码”255.255.255.0“ 网关地址”10.16.3.1“。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">S7-1200 CP卡的IP地址为”10.18.61.8/23“，子网掩码”255.255.254.0“ 网关地址”10.18.60.1“。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">通信的两个设备不在同一个IP子网中，需要通过华为超融合网络的路由器来实现数据的路由转发。从S7通信的角度看，此时KEPServer 为S7的客户端，S7-1200 PLC为S7服务器。我们对照着理论部分的TCP建立过程来看S7通信建立的TCP的建立过程。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">先看在KEPServer S7客户端抓包文件，分析如下图：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505741038616288953510.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="333" src="/upload/image/20231114/1699959381953007.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">再看再PLC S7服务器端的抓包文件，分析如下图：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505742930244152939666.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="312" src="/upload/image/20231114/1699959382971905.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">问题就出现在TCP的三次握手的第三次，从KEPServer端看发出正常的ACK=1的确认包，而当通过网络转发给PLC的时候，该包被修改，除了原来ACK=1外又被修改RST=1，源发送者可没有发送RST=1。换句话说，PLC的三次握手的最后一次没有正常，所以PLC的TCP连接没有进入到TCP连接建立的状态，也就是所谓的TCP半连接状态。PLC的TCP既然没有完全建立成功，所以发送过来的任何的应用层请求连接都会被PLC发送RST=1的包。可以用下图来示意上面的连接过程：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505745964849487203269.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="347" src="/upload/image/20231114/1699959382695501.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">对于客户端已经完成了三次握手，所以客户端的TCP状态机已经进入到了 “ESTABLISHED“状态；而对服务器端由于没有正确收到 ACK的报文，而是收到ACK和RST同时为1的包，所以服务器端的TCP状态机只是进入到了 ”SYN-RCVD“状态，没有进入到下一个状态 ”ESTABLISHED“。这是造成现场问题的正真原因。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">我们再对比两端的三次握手的数据帧：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">第一次握手的数据包对比：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505748502046353084397.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="342" src="/upload/image/20231114/1699959383137912.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505753180871578292005.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="185" src="/upload/image/20231114/1699959383188606.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">我们发现端口号，发送序列号和确认序列号及TCP标志位都一致。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">第二次握手的数据包对比：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505867757557439754840.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="356" src="/upload/image/20231114/1699959384260552.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505871568913801711526.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="197" src="/upload/image/20231114/1699959384150839.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">我们发现端口号，发送序列号和确认序列号及TCP标志位也都一致。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">第三次握手的数据包对比：<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505874591956676475897.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="354" src="/upload/image/20231114/1699959384614448.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"> <p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);"><a target="_blank" href="https://www.ad.siemens.com.cn/club/bbs/upload/image/20231108/6383505875086090808399882.png" style="box-sizing: border-box; padding: 0px; margin: 0px; color: rgb(50, 50, 50); outline: 0px; background-color: transparent; cursor: pointer; border: none; text-decoration-line: none !important;"><img width="528" height="206" src="/upload/image/20231114/1699959385978495.png" style="box-sizing: border-box; font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, "Noto Sans CJK SC", "WenQuanYi Micro Hei", Arial, sans-serif; padding: 0px; margin: 0px; border: 0px; vertical-align: middle;"/></a><p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">我们发现端口号，发送序列号和确认序列号一致，但TCP标志位发生了改变。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">从这个案例可以看到理论知识的重要性，只有掌握了理论知识才能在现场解决所谓的疑难的问题，原因是你“有理有据“。<p style="box-sizing: border-box; font-family: "Noto Sans SC", "Microsoft YaHei", ΢��ź�, -apple-system, BlinkMacSystemFont, "segoe ui", Roboto; padding: 0px; margin-top: 0px; margin-bottom: 0px; color: rgb(0, 0, 40); text-align: justify; font-size: 14px; line-height: 26px; text-wrap: wrap; background-color: rgb(255, 255, 255);">希望这篇文章给大家帮助！也希望大家可以进一步探讨。

网络协议详解TCP协议

马上注册，结交更多好友，享用更多功能，让你轻松玩转社区。

回复

浏览过的版块