feat: Computer network exps (#22)
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@ -4,3 +4,5 @@ title: 计算机网络
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!!! warning "施工中"
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!!! warning "施工中"
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---
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title: 计算机网络实践
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---
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## 2023-2024学年上学期
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### 刘献忠
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- 实验比较简单, 要求也比隔壁班低, 最后一个 socket lab 作业要求也比隔壁低
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- [SOCKET_LAB](https://github.com/KirisameVanilla/SOCKET_LAB)
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### 王廷
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- 听我同学说实验比较难
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## 2024-2025学年上学期
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### 王廷
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#### 实验报告
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除第一个实验外，其余实验所用到的 `.pcapng` 文件均附在对应文件夹下
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- [lab1](./lab/lab1/lab1.md)
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- [lab2 Ethernet](./lab/lab2/lib2)
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- [lab3 IPV4](./lab/lab3/lib3)
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- [lab4 ARP](./lab/lab4/lib4)
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- [lab5 UDP](./lab/lab5/lib5)
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- [lab6 TCP](./lab/lab6/lib6)
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- [lab7 Socket Programming](./lab/lab7/lib7)
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---
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title: Lab1
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---
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# 华东师范大学软件学院实验报告
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## 一、实验目的
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1. 学会使用curl与wget指令
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2. 学会通过Wireshark获取数据包
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3. 了解协议层数据包的结构
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4. 学会计算并分析协议开销
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## 二、实验内容与实验步骤
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1. 在控制台中输入`curl http://1st.moe/`，并观察到`200 OK`
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2. 启动Wireshark，选择监听以太网，并将捕获过滤器设置为tcp port 80，关闭混杂模式，并启用"enable network name resolution"选项
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3. 关闭所有浏览器窗口后开始捕获
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4. 重新在控制台输入 `curl http://1st.moe/`
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5. 停止Wireshark捕获
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## 三、实验环境
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B226机房电脑
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## 四、实验过程与分析
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1. 实验过程
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捕获内容如图所示
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2.
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分析协议包的内容
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根据如上四张图片，可以发现各个协议所占的字节数为
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| 协议 | 字节数 |
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|-------------------------------------|-----------|
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| Ethernet (eth) | 14 bytes |
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| Internet Protocol Version 6 (ipv6) | 40 bytes |
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| Transmission Control Protocol (tcp) | 20 bytes |
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| Hypertext Transfer Protocol (http) | 128 bytes |
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则包的结构大致如下
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| eth | ip | tcp | http |
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|-----------------|------------------|----------|-----------|
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| 14 bytes | 40 bytes | 20 bytes | 128 bytes |
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| Ethernet Header | Ethernet Payload | | |
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| IP Header | IP Payload | | |
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3. 问题
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1. 分析协议开销
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一个GET本身的大小为128
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bytes，而其相应产生的SYN、ACK请求也应算入其开销中。根据图片
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可以计算得出由于协议产生的总开销为86+74+(202-128)+74=308
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bytes，从而计算得出比值约为0.4156，考虑到信息传输的稳定性，协议开销是值得的。
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2. 以太网头部中哪一部分是解复用键并且告知它的下一个高层指的是IP，在这一包内哪一个值可以表示IP
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根据图片
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可以直观看出ipv6对应的分解键为0x86dd，tcp对应的分解键为6
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4. 故障分析
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在实验过程中出现了控制台有反馈但Wireshark没有捕获的情况，经排查后发现是由于控制台指令输入错误：误将http输入为https所致。
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## 五、实验结果总结
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1. 实验完成了对一个HTTP包的拆解与分析，其大体结构大致如下
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|th|ip|tcp|http|
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|-|-|--|-|
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| 14 bytes | 40 bytes | 20 bytes | 128 bytes |
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| Ethernet Header | Ethernet Payload | | |
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| IP Header | IP Payload | | |
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2. 实验通过curl指令与Wireshark软件完成，在其中熟悉网络工具的使用，并体会到其强大之处
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3. 通过查询相关资料，了解开销、分解键等概念
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---
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title: Lab2 - Ethernet
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---
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# 华东师范大学软件学院实验报告
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## 一、实验目的
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学习以太网帧的组成
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## 二、使用内容与实验步骤
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1. 捕获帧
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1. 对一个远程服务器使用 ping 指令发送信息，并检查是否有回复；
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2. 启动 Wireshark ，选择过滤 icmp ，开启“启用 MAC 名称解析”选项，开始捕获以太网帧；
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3. 重复第一步；
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4. 终止 ping 指令，返回 Wireshark 并停止捕获。
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2. 检查捕获到的数据
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1. 选择捕获到的任意数据包，查看其结构与组成数据包字节的详细信息；
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2. 展开以太网报头字段并查看详细信息。
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3. 以太网帧结构
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绘制一个显示以太网头字段位置与大小的 ping 报文图。
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4. 以太网地址范围
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绘制一张图，显示电脑、路由器、远程服务器的相对位置。
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用以太网地址标注计算机与路由器，IP 地址标注计算机与远程服务器。
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并显示以太网和互联网其他部分在图中的位置。
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5. 广播帧
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启动 Wireshark ，选择过滤 ether multicast ，等待一段时间，捕获广播与组播以太网帧，并根据结果完成以下两个任务：
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1. 找到广播以太网地址
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2. 找到以太网地址的哪一位确认是单播还是组播
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## 三、实验环境
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- 实验仪器：ThinkPad X230i
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- 操作系统：Arch GNU/Linux x86\_64
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- 以太网控制器：Intel Corporation 82575LM Gigabit Network Connection
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- 网络控制器：Realtek Semiconductor Co., Ltd. RTL8188CE 820.11b/g/n WiFi Adapter
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- 网络连接：校园网ECNU-1X
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## 四、实验过程与分析
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1. 捕获帧
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2. 检查捕获到的数据
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3. 以太网帧结构
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<table>
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<tr>
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<td align="center" colspan='3'>Ethernet II</td>
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<td align="center">IP&ICMP</td>
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</tr>
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<tr>
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<td align="center">Destination</td>
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<td align="center">Source</td>
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<td align="center">Type</td>
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<td align="center" rowspan='2'>60 Bytes</td>
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</tr>
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<tr>
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<td align="center">6 Bytes</td>
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<td align="center">6 Bytes</td>
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<td align="center">2 Bytes</td>
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</tr>
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<tr>
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<td align="center" colspan='3'>Ethernet Header</td>
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<td align="center">Ethernet Payload</td>
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</tr>
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</table>
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4. 以太网地址范围
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5. 广播帧
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捕获内容如图：
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1. 以太网地址为 ff:ff:ff:ff:ff:ff，在 Wireshark 中标注为 Broadcast
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2. 第一个字节的末位为1是组播，反之则是单播，所有比特均为1则是广播
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## 五、试验结果总结
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在本次实验中，我顺利地完成了各项任务，了解并学习到了以太网传输的各项细节
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traceroute to 1st.moe (52.74.232.59), 30 hops max, 60 byte packets
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1 * * *
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2 10.100.5.1 (10.100.5.1) 8.795 ms 8.962 ms 9.096 ms
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3 202.120.95.246 (202.120.95.246) 9.451 ms 9.092 ms 9.243 ms
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4 202.120.95.254 (202.120.95.254) 12.480 ms 12.777 ms 13.331 ms
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5 10.255.16.1 (10.255.16.1) 12.974 ms 13.249 ms 12.734 ms
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6 10.255.249.253 (10.255.249.253) 12.382 ms 11.127 ms 11.127 ms
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7 10.255.38.254 (10.255.38.254) 10.087 ms 9.632 ms 9.452 ms
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8 202.112.27.13 (202.112.27.13) 9.268 ms 6.546 ms 6.331 ms
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9 101.4.117.58 (101.4.117.58) 6.248 ms 9.316 ms 9.147 ms
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10 * * *
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11 101.4.115.250 (101.4.115.250) 37.316 ms 37.288 ms 36.908 ms
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12 * * *
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13 * * 101.4.114.194 (101.4.114.194) 33.724 ms
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14 101.4.114.170 (101.4.114.170) 38.219 ms 101.4.117.102 (101.4.117.102) 44.767 ms 44.589 ms
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15 101.4.114.222 (101.4.114.222) 67.753 ms 67.658 ms 63.246 ms
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16 203.131.254.213 (203.131.254.213) 85.750 ms 85.593 ms 85.431 ms
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17 203.131.242.222 (203.131.242.222) 67.546 ms 67.933 ms 67.157 ms
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18 52.93.157.242 (52.93.157.242) 67.671 ms 52.93.157.226 (52.93.157.226) 67.991 ms 68.002 ms
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19 52.93.35.125 (52.93.35.125) 67.392 ms 52.93.35.109 (52.93.35.109) 68.086 ms 52.93.35.35 (52.93.35.35) 68.009 ms
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20 * * *
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21 * * *
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22 * * *
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23 * * *
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24 * * *
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25 * * *
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26 * * *
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27 * * *
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28 * * *
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29 * * *
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30 * * *
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---
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title: Lab3 - IPv4
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---
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# 华东师范大学软件学院实验报告
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## 一、实验目的
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学习 IP 协议的相关内容
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## 二、使用内容与实验步骤
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1. 捕获轨迹
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1. 对一个远程服务器使用 wget/curl 指令，并检查是否成功；
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2. 对同一远程服务器使用 traceroute 指令，查看访问的路径；
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3. 启动 Wireshark ，选择过滤 tcp port 80 ，并勾选“启用网络名称检查”
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4. 重复第一步
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5. 返回 Wireshark ，停止捕获。
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2. 检查捕获到的数据
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1. 选择任意捕获到的数据包，查看其结构与组成数据包字节的详细信息；
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2. 展开 IP 报头字段并查看详细信息。
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3. IP 结构
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1. 绘制一个 IP 字段位置与大小的报文图
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2. 回答下列问题
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1. 电脑与远程服务端的 IP 地址分别是多少？
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2. 总长字段包括 IP 报头与 IP 负载还是仅计算 IP 负载？
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3. 对于不同数据包，标识字段的值是不同还是相同？
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4. 电脑发送的数据包的 TTL 字段的初始值是什么？是最大可能值还是一个较小的值？
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5. 如何通过查看数据包确认其是否被分段？
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6. IP 报头长度是多少，它如何在报头字段中编码？
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4. IP 路径
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绘制 1.2 步骤中访问的路径
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5. IP 报头校验
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通过如下步骤检验 IP 报头校验和是否正确
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1. 将报头划分为等长的 10 段，每段长度为 2 个字节，将其视为 10 个十六进制数字；
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2. 将 10 个 16 进制数字相加，计算他们的和；
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3. 将得到的和分为两段，使得其中的一段为最右边的 4 位 16 进制数，计算两段之和；
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4. 检查结果是否为 0xffff 。
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## 三、实验环境
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- 实验仪器：ThinkPad X230i
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- 操作系统：Arch GNU/Linux x86\_64
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- 以太网控制器：Intel Corporation 82575LM Gigabit Network Connection
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- 网络控制器：Realtek Semiconductor Co., Ltd. RTL8188CE 820.11b/g/n WiFi Adapter
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- 网络连接：校园网ECNU-1X
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||||||
|
## 四、实验过程与分析
|
||||||
|
|
||||||
|
1. 捕获轨迹
|
||||||
|
|
||||||
|
traceroute 获取到的信息如下：
|
||||||
|
|
||||||
|
``` bash
|
||||||
|
traceroute to 1st.moe (52.74.232.59), 30 hops max, 60 byte packets
|
||||||
|
1 * * *
|
||||||
|
2 10.100.5.1 (10.100.5.1) 8.795 ms 8.962 ms 9.096 ms
|
||||||
|
3 202.120.95.246 (202.120.95.246) 9.451 ms 9.092 ms 9.243 ms
|
||||||
|
4 202.120.95.254 (202.120.95.254) 12.480 ms 12.777 ms 13.331 ms
|
||||||
|
5 10.255.16.1 (10.255.16.1) 12.974 ms 13.249 ms 12.734 ms
|
||||||
|
6 10.255.249.253 (10.255.249.253) 12.382 ms 11.127 ms 11.127 ms
|
||||||
|
7 10.255.38.254 (10.255.38.254) 10.087 ms 9.632 ms 9.452 ms
|
||||||
|
8 202.112.27.13 (202.112.27.13) 9.268 ms 6.546 ms 6.331 ms
|
||||||
|
9 101.4.117.58 (101.4.117.58) 6.248 ms 9.316 ms 9.147 ms
|
||||||
|
10 * * *
|
||||||
|
11 101.4.115.250 (101.4.115.250) 37.316 ms 37.288 ms 36.908 ms
|
||||||
|
12 * * *
|
||||||
|
13 * * 101.4.114.194 (101.4.114.194) 33.724 ms
|
||||||
|
14 101.4.114.170 (101.4.114.170) 38.219 ms 101.4.117.102 (101.4.117.102) 44.767 ms 44.589 ms
|
||||||
|
15 101.4.114.222 (101.4.114.222) 67.753 ms 67.658 ms 63.246 ms
|
||||||
|
16 203.131.254.213 (203.131.254.213) 85.750 ms 85.593 ms 85.431 ms
|
||||||
|
17 203.131.242.222 (203.131.242.222) 67.546 ms 67.933 ms 67.157 ms
|
||||||
|
18 52.93.157.242 (52.93.157.242) 67.671 ms 52.93.157.226 (52.93.157.226) 67.991 ms 68.002 ms
|
||||||
|
19 52.93.35.125 (52.93.35.125) 67.392 ms 52.93.35.109 (52.93.35.109) 68.086 ms 52.93.35.35 (52.93.35.35) 68.009 ms
|
||||||
|
20 * * *
|
||||||
|
21 * * *
|
||||||
|
22 * * *
|
||||||
|
23 * * *
|
||||||
|
24 * * *
|
||||||
|
25 * * *
|
||||||
|
26 * * *
|
||||||
|
27 * * *
|
||||||
|
28 * * *
|
||||||
|
29 * * *
|
||||||
|
30 * * *
|
||||||
|
```
|
||||||
|
|
||||||
|
2. 
|
||||||
|
|
||||||
|
3.
|
||||||
|
1. IP结构
|
||||||
|
<table align="center">
|
||||||
|
<tr>
|
||||||
|
<td align="center" colspan='12'>IP</td>
|
||||||
|
<td align="center">TCP</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td align="center">Version</td>
|
||||||
|
<td align="center">Header Length</td>
|
||||||
|
<td align="center">Differentiated Services Field</td>
|
||||||
|
<td align="center">Total Length</td>
|
||||||
|
<td align="center">Identification</td>
|
||||||
|
<td align="center">Flags</td>
|
||||||
|
<td align="center">Fragment Offset</td>
|
||||||
|
<td align="center">TTL</td>
|
||||||
|
<td align="center">Protocal</td>
|
||||||
|
<td align="center">Header Checksum</td>
|
||||||
|
<td align="center">Source Address</td>
|
||||||
|
<td align="center">Destinatoin Address</td>
|
||||||
|
<td align="center" rowspan='2'>32 Bytes</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td align="center">4 bits</td>
|
||||||
|
<td align="center">4 bits</td>
|
||||||
|
<td align="center">1 Byte</td>
|
||||||
|
<td align="center">2 Bytes</td>
|
||||||
|
<td align="center">2 Bytes</td>
|
||||||
|
<td align="center">3 bits</td>
|
||||||
|
<td align="center">13 Bits</td>
|
||||||
|
<td align="center">1 Byte</td>
|
||||||
|
<td align="center">1 Byte</td>
|
||||||
|
<td align="center">2 Bytes</td>
|
||||||
|
<td align="center">4 Bytes</td>
|
||||||
|
<td align="center">4 Bytes</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td align="center" colspan='12'>Ethernet Header</td>
|
||||||
|
<td align="center">Ethernet Payload</td>
|
||||||
|
</tr>
|
||||||
|
</table>
|
||||||
|
2.
|
||||||
|
1. 服务端 IP 地址为 52.74.232.59；电脑 IP 地址为 172.30.218.6
|
||||||
|
2. 总长字段为 52 = 20 + 32 ，所以计算时包含 IP 报头与 IP 负载
|
||||||
|
3. 不同
|
||||||
|
4. 电脑发送的 TTL 值为 38 ，是一个较小的值
|
||||||
|
5. 通过查看 Flags 字段
|
||||||
|
6. 长度为 20 Bytes ，编码在 IP 报头第一个字节的 4~8 位
|
||||||
|
4.
|
||||||
|
|
||||||
|
5. 执行如下代码：
|
||||||
|
|
||||||
|
``` c
|
||||||
|
#include<bits/stdc++.h>
|
||||||
|
|
||||||
|
using namespace std;
|
||||||
|
|
||||||
|
int main()
|
||||||
|
{
|
||||||
|
printf("%x",0x4500+0x0034+0xd124+0x4000+0x2606+0xe0f4+0x344a+0xe83b+0xda06+0xac1e);
|
||||||
|
return 0;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
其结果为0x4fffb，计算4+fffb=ffff，故正确。
|
||||||
Binary file not shown.
Binary file not shown.
|
|
@ -0,0 +1 @@
|
||||||
|
_gateway (172.31.0.1) at 54:c6:ff:7b:38:02 [ether] on wlan0
|
||||||
|
|
@ -0,0 +1 @@
|
||||||
|
No ARP entry for 172.31.0.1
|
||||||
|
|
@ -0,0 +1,26 @@
|
||||||
|
enp0s25: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
|
||||||
|
ether 3c:97:0e:27:a3:96 txqueuelen 1000 (Ethernet)
|
||||||
|
RX packets 0 bytes 0 (0.0 B)
|
||||||
|
RX errors 0 dropped 0 overruns 0 frame 0
|
||||||
|
TX packets 0 bytes 0 (0.0 B)
|
||||||
|
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
|
||||||
|
device interrupt 20 memory 0xf2500000-f2520000
|
||||||
|
|
||||||
|
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
|
||||||
|
inet 127.0.0.1 netmask 255.0.0.0
|
||||||
|
inet6 ::1 prefixlen 128 scopeid 0x10<host>
|
||||||
|
loop txqueuelen 1000 (Local Loopback)
|
||||||
|
RX packets 1511 bytes 158325 (154.6 KiB)
|
||||||
|
RX errors 0 dropped 0 overruns 0 frame 0
|
||||||
|
TX packets 1511 bytes 158325 (154.6 KiB)
|
||||||
|
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
|
||||||
|
|
||||||
|
wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
|
||||||
|
inet 172.31.215.159 netmask 255.255.0.0 broadcast 172.31.255.255
|
||||||
|
inet6 fe80::eb67:d196:62b:626a prefixlen 64 scopeid 0x20<link>
|
||||||
|
ether e0:06:e6:c4:be:04 txqueuelen 1000 (Ethernet)
|
||||||
|
RX packets 4206 bytes 2310892 (2.2 MiB)
|
||||||
|
RX errors 0 dropped 0 overruns 0 frame 0
|
||||||
|
TX packets 4771 bytes 2531632 (2.4 MiB)
|
||||||
|
TX errors 0 dropped 76 overruns 0 carrier 0 collisions 0
|
||||||
|
|
||||||
Binary file not shown.
|
After Width: | Height: | Size: 162 KiB |
Binary file not shown.
|
After Width: | Height: | Size: 126 KiB |
Binary file not shown.
|
After Width: | Height: | Size: 142 KiB |
|
|
@ -0,0 +1,111 @@
|
||||||
|
---
|
||||||
|
title: Lab4 - ARP
|
||||||
|
---
|
||||||
|
|
||||||
|
# 华东师范大学软件学院实验报告
|
||||||
|
|
||||||
|
## 一、实验目的
|
||||||
|
|
||||||
|
了解 ARP 的工作原理。
|
||||||
|
|
||||||
|
## 二、使用内容与实验步骤
|
||||||
|
|
||||||
|
1. 捕获
|
||||||
|
1. 使用`ifconfig`指令查找电脑的以太网地址。
|
||||||
|
2. 使用`route`指令查看默认网关 ip 地址。
|
||||||
|
3. 启动 Wireshark ，将过滤器设置为`arp`，开始捕获。
|
||||||
|
4. 使用`arp -a`指令查看 ARP 缓存，并使用`sudo arp -d 网关ip地址`从缓存中清除默认网关。
|
||||||
|
5. 使用浏览器浏览网页一段时间。
|
||||||
|
6. 在捕获到 arp 流量后停止捕获。
|
||||||
|
2. 检查捕获
|
||||||
|
1. 将页面内的过滤器设置为`eth.addr == 电脑以太网地址`。
|
||||||
|
2. 查看捕获到的内容
|
||||||
|
3. ARP 请求与应答
|
||||||
|
绘制计算机与默认网关之间发送 ARP 请求与回复数据包的图解。
|
||||||
|
4. 以太网上的 ARP 详细信息
|
||||||
|
回答以下问题
|
||||||
|
1. 什么操作码用于请求，什么操作码用于回复。
|
||||||
|
2. 请求的 ARP 报头有多大？回复的 ARP 报头有多大？
|
||||||
|
3. 对于未知目标 MAC 地址的请求中携带什么值？
|
||||||
|
4. 什么以太网类型值表明 ARP 是更高级协议？
|
||||||
|
5. ARP 回复是否为广播？
|
||||||
|
|
||||||
|
## 三、实验环境
|
||||||
|
|
||||||
|
- 实验仪器：ThinkPad X230i
|
||||||
|
- 操作系统：Arch GNU/Linux x86\_64
|
||||||
|
- 以太网控制器：Intel Corporation 82575LM Gigabit Network Connection
|
||||||
|
- 网络控制器：Realtek Semiconductor Co., Ltd. RTL8188CE 820.11b/g/n WiFi Adapter
|
||||||
|
- 网络连接：校园网ECNU-1X
|
||||||
|
|
||||||
|
## 四、实验过程与分析
|
||||||
|
|
||||||
|
1. 捕获
|
||||||
|
1. 执行`ifconfig`指令，得到的输出如下：
|
||||||
|
|
||||||
|
``` bash
|
||||||
|
enp0s25: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
|
||||||
|
ether 3c:97:0e:27:a3:96 txqueuelen 1000 (Ethernet)
|
||||||
|
RX packets 0 bytes 0 (0.0 B)
|
||||||
|
RX errors 0 dropped 0 overruns 0 frame 0
|
||||||
|
TX packets 0 bytes 0 (0.0 B)
|
||||||
|
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
|
||||||
|
device interrupt 20 memory 0xf2500000-f2520000
|
||||||
|
|
||||||
|
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
|
||||||
|
inet 127.0.0.1 netmask 255.0.0.0
|
||||||
|
inet6 ::1 prefixlen 128 scopeid 0x10<host>
|
||||||
|
loop txqueuelen 1000 (Local Loopback)
|
||||||
|
RX packets 1511 bytes 158325 (154.6 KiB)
|
||||||
|
RX errors 0 dropped 0 overruns 0 frame 0
|
||||||
|
TX packets 1511 bytes 158325 (154.6 KiB)
|
||||||
|
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
|
||||||
|
|
||||||
|
wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
|
||||||
|
inet 172.31.215.159 netmask 255.255.0.0 broadcast 172.31.255.255
|
||||||
|
inet6 fe80::eb67:d196:62b:626a prefixlen 64 scopeid 0x20<link>
|
||||||
|
ether e0:06:e6:c4:be:04 txqueuelen 1000 (Ethernet)
|
||||||
|
RX packets 4206 bytes 2310892 (2.2 MiB)
|
||||||
|
RX errors 0 dropped 0 overruns 0 frame 0
|
||||||
|
TX packets 4771 bytes 2531632 (2.4 MiB)
|
||||||
|
TX errors 0 dropped 76 overruns 0 carrier 0 collisions 0
|
||||||
|
```
|
||||||
|
|
||||||
|
在 `wlan0` 下的 `ether` 一行可以得知计算机以太网地址为 `e0:06:e6:c4:be:04` 。
|
||||||
|
2. 执行 `route` 指令，得到的输出如下：
|
||||||
|
|
||||||
|
```
|
||||||
|
Kernel IP routing table
|
||||||
|
Destination Gateway Genmask Flags Metric Ref Use Iface
|
||||||
|
default _gateway 0.0.0.0 UG 600 0 0 wlan0
|
||||||
|
172.31.0.0 0.0.0.0 255.255.0.0 U 600 0 0 wlan0
|
||||||
|
```
|
||||||
|
|
||||||
|
可以得知默认网关的 ip 地址为 `172.31.0.0` 。
|
||||||
|
3. 启动捕获。
|
||||||
|
4. 执行 `arp -a` 指令，得到输出 `_gateway (172.31.0.1) at 54:c6:ff:7b:38:02 [ether] on wlan0` 。随后执行 `sudo arp -d 172.31.0.1` 指令清除缓存，该指令没有输出，若重复执行，则会得到 `No ARP entry for 172.31.0.1` 输出。
|
||||||
|
5. 在观察到已经捕获 7 个 ARP 流量包后停止捕获，其界面如图：
|
||||||
|
|
||||||
|
2. 检查捕获
|
||||||
|
*因为捕获到的包数量较少，故不设置过滤器。*
|
||||||
|
请求包：
|
||||||
|
|
||||||
|
回复包：
|
||||||
|
|
||||||
|
3. ARP 请求与回复
|
||||||
|
其图例如下
|
||||||
|
|
||||||
|
```mermaid
|
||||||
|
flowchart LR
|
||||||
|
computer[计算机<br>MAC e0:06:e6:c4:be:04<br>IP 172.31.215.159]
|
||||||
|
gateway[网关<br>MAC 54:c6:ff:7b:38:02<br>IP 172.31.0.1]
|
||||||
|
computer--request<br>Who has 172.31.0.1? Tell 172.31.215.159-->gateway
|
||||||
|
gateway--reply<br>172.31.0.1 is at <font color="red"><b>54:c6:ff:7b:38:02</b></font>-->computer
|
||||||
|
```
|
||||||
|
|
||||||
|
4. 以太网上的 ARP 详细信息
|
||||||
|
1. 请求的操作码为 `0x0001` ，回复的操作码为 `0x0002` 。
|
||||||
|
2. 请求与回复的的 ARP 报头均为 28 bytes，对于报文，请求的报文为 42 bytes，回复的报文为60 bytes。
|
||||||
|
3. 目标 MAC 地址为 `00:00:00_00:00:00` 。
|
||||||
|
4. 以太网报头中的 `type` 字段为 `0x0806` 。
|
||||||
|
5. ARP 回复为单播而非广播。
|
||||||
|
|
@ -0,0 +1,4 @@
|
||||||
|
Kernel IP routing table
|
||||||
|
Destination Gateway Genmask Flags Metric Ref Use Iface
|
||||||
|
default _gateway 0.0.0.0 UG 600 0 0 wlan0
|
||||||
|
172.31.0.0 0.0.0.0 255.255.0.0 U 600 0 0 wlan0
|
||||||
Binary file not shown.
|
After Width: | Height: | Size: 321 KiB |
Binary file not shown.
|
After Width: | Height: | Size: 107 KiB |
Binary file not shown.
|
After Width: | Height: | Size: 124 KiB |
Binary file not shown.
|
After Width: | Height: | Size: 109 KiB |
|
|
@ -0,0 +1,80 @@
|
||||||
|
---
|
||||||
|
title: Lab5 - UDP
|
||||||
|
---
|
||||||
|
# 华东师范大学软件学院实验报告
|
||||||
|
|
||||||
|
## 一、实验目的
|
||||||
|
|
||||||
|
学习 UDP 的构成等详细信息。
|
||||||
|
|
||||||
|
## 二、使用内容与实验步骤
|
||||||
|
|
||||||
|
1. 捕获
|
||||||
|
1. 启动 Wireshark ，关闭混杂，将过滤器设置为“udp”，开始捕获。
|
||||||
|
2. 浏览网页以产生 UDP 流量。
|
||||||
|
3. 停止浏览，等待一分钟左右观察背景 UDP 流量。
|
||||||
|
4. 停止捕获。
|
||||||
|
2. 检查捕获到的数据
|
||||||
|
观察所捕获到的流量包，UDP 协议包包括如下字段：源端口、目标端口、长度、校验和。
|
||||||
|
**注意：协议列所列出的协议可能是 UDP 之上的应用程序协议名称而非 UDP**
|
||||||
|
3. UDP 消息结构
|
||||||
|
制作一份 UDP 报文图例并回答如下问题：
|
||||||
|
1. 长度字段包含什么？
|
||||||
|
1. UDP 有效负载
|
||||||
|
2. UDP 有效负载与 UDP 报头
|
||||||
|
3. UDP 有效负载、UDP 报头与底层报头
|
||||||
|
2. UDP 校验和的长度为多少？（以位为单位）
|
||||||
|
3. UDP 报头的长度为多少字节？
|
||||||
|
4. UDP 使用
|
||||||
|
回答如下问题：
|
||||||
|
1. 给出标识上层协议为 UDP 的 IP 协议字段的值
|
||||||
|
2. 检查 UDP 消息并提供**当电脑既不是源IP地址也不是目标IP地址时**使用的目标 IP 地址
|
||||||
|
3. 捕获到的 UDP 消息的典型大小为多少
|
||||||
|
|
||||||
|
## 三、实验环境
|
||||||
|
|
||||||
|
- 实验仪器：ThinkPad X230i
|
||||||
|
- 操作系统：Arch GNU/Linux x86\_64
|
||||||
|
- 以太网控制器：Intel Corporation 82575LM Gigabit Network Connection
|
||||||
|
- 网络控制器：Realtek Semiconductor Co., Ltd. RTL8188CE 820.11b/g/n WiFi Adapter
|
||||||
|
- 网络连接：校园网ECNU-1X
|
||||||
|
|
||||||
|
## 四、实验过程与分析
|
||||||
|
|
||||||
|
1. 捕获
|
||||||
|
本步骤采用老师所提供的捕获文件
|
||||||
|
2. 检查捕获到的数据
|
||||||
|
捕获包如图所示
|
||||||
|
|
||||||
|
3. UDP 消息结构
|
||||||
|
观察下图所列出的包
|
||||||
|
|
||||||
|
1. UDP 报头为 8 bytes，负载为 143 bytes，二者之和恰为 UDP 长度字段所标注的 151 bytes，故 UDP 长度字段包括 **UDP 有效负载与 UDP 报头**。
|
||||||
|
2. UDP 校验和的长度为 2 bytes，即 16 位。
|
||||||
|
3. UDP 报头的长度为 8 bytes。
|
||||||
|
UDP 报文结构如下表所示：
|
||||||
|
<table align="center">
|
||||||
|
<tr>
|
||||||
|
<td align="center" colspan='4'>UDP Header</td>
|
||||||
|
<td align="center">UDP Payload</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td align="center">Source Port</td>
|
||||||
|
<td align="center"> Destination Port</td>
|
||||||
|
<td align="center">Length</td>
|
||||||
|
<td align="center">Checksum</td>
|
||||||
|
<td align="center" rowspan='2'> many bytes</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
</tr>
|
||||||
|
</table>
|
||||||
|
4. UDP 使用
|
||||||
|
1. 如图所示，IP 协议字段的值为 0x11 ，即 17
|
||||||
|
|
||||||
|
2. 如图所示，目标 IP 地址为 239.255.255.250
|
||||||
|
|
||||||
|
3. 捕获到的 UDP 消息大小大多在 100 bytes 与 300 bytes 之间。
|
||||||
Binary file not shown.
|
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|
After Width: | Height: | Size: 274 KiB |
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|
After Width: | Height: | Size: 193 KiB |
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|
After Width: | Height: | Size: 180 KiB |
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|
After Width: | Height: | Size: 126 KiB |
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|
After Width: | Height: | Size: 132 KiB |
|
|
@ -0,0 +1,234 @@
|
||||||
|
---
|
||||||
|
title: Lab6 - TCP
|
||||||
|
---
|
||||||
|
|
||||||
|
# 华东师范大学软件学院实验报告
|
||||||
|
|
||||||
|
## 一、实验目的
|
||||||
|
|
||||||
|
学习了解 TCP 的相关内容。
|
||||||
|
|
||||||
|
## 二、使用内容与实验步骤
|
||||||
|
|
||||||
|
1. 捕获
|
||||||
|
|
||||||
|
1. 找到一个可以使用 HTTP 下载的中等大小单一资源。
|
||||||
|
|
||||||
|
2. 使用 wget 或 curl 命令尝试下载，确保可以在几秒内下载至少 500 KB 的内容。
|
||||||
|
|
||||||
|
3. 启用 Wireshark ，将过滤器设置为 "tcp and host $DOMAIN" ，其中 $DOMAIN 为远程服务器的域名，并开始捕获。
|
||||||
|
|
||||||
|
4. 重复 1.2 中的命令。
|
||||||
|
|
||||||
|
5. 返回 Wireshark 并停止捕获。
|
||||||
|
|
||||||
|
2. 检查捕获到的内容
|
||||||
|
|
||||||
|
选择一个协议列为 TCP 的数据包，展开 TCP 协议部分。捕获到的内容中协议列除了初始 HTTP GET 和末尾的 HTTP 相应包之外均为 TCP 。在一个 TCP 包中，大致可以看到如下内容：
|
||||||
|
|
||||||
|
1. 源端口（可能为 80）与目标端口。
|
||||||
|
|
||||||
|
2. 序列号字段，告知第一个有效负载字节在字节流中的位置。
|
||||||
|
|
||||||
|
3. 确认字段，告知反向字节流中最后接收的位置。
|
||||||
|
|
||||||
|
4. 报头长度，TCP 报头的长度。
|
||||||
|
|
||||||
|
5. 标志字段。
|
||||||
|
|
||||||
|
6. 校验和，用于检查传输错误。
|
||||||
|
|
||||||
|
7. 选项字段。（可能不存在）
|
||||||
|
|
||||||
|
8. TCP 有效负载，表示正在传输的内容.（可能不存在）
|
||||||
|
|
||||||
|
3. TCP 段结构
|
||||||
|
|
||||||
|
绘制一个 TCP 段结构图。
|
||||||
|
|
||||||
|
4. TCP 建立与拆除。
|
||||||
|
|
||||||
|
- 三次握手
|
||||||
|
|
||||||
|
查找带有 SYN 标志的 TCP 段以及其后的数据包的详细信息。绘制三次握手的时间序列图，序列图应包括如下内容：
|
||||||
|
|
||||||
|
- 每个段上的序列号与 ACK 号（如果存在）
|
||||||
|
|
||||||
|
- 以毫秒为单位的时间
|
||||||
|
|
||||||
|
- 到服务器的往返时间估计，即 SYN 和 SYN-ACK 段之间的差值
|
||||||
|
|
||||||
|
- 连接选项
|
||||||
|
|
||||||
|
SYN 数据包中携带了哪些 TCP 选项。
|
||||||
|
|
||||||
|
- FIN/RST 拆除
|
||||||
|
|
||||||
|
查找带有 FIN 或 RES 标志的 TCP 段及其之后的数据包的详细信息。并绘制时间序列图，要求同三次握手的时间序列图。
|
||||||
|
|
||||||
|
5. TCP 数据传输
|
||||||
|
|
||||||
|
在统计菜单下，选择“IO图表”，观察并回答以下问题：
|
||||||
|
|
||||||
|
1. TCP 连接运行良好后，下载方向的大致数据速率是多少（分别计算 packets/s 与 bits/s）
|
||||||
|
|
||||||
|
2. 查看下载数据包，通过观察包的大小与 TCP 有效负载的大小，计算下载率中有多少百分比是内容？
|
||||||
|
|
||||||
|
3. 传输方向的大致数据速率是多少？
|
||||||
|
|
||||||
|
4. 如果最近从服务器接收的 TCP 段的序列号为 x ，那么下一个传输的 TCP 段携带什么 ACK 号？
|
||||||
|
|
||||||
|
检查捕获到的下载数据包是否具有如下特征：
|
||||||
|
|
||||||
|
- 延迟 ACK。
|
||||||
|
|
||||||
|
- 接受到的段的序列号增加，后续传输的段的 ACK 号也相应增加。
|
||||||
|
|
||||||
|
- 在初始获取之后，传输的段的序列号不增加，接收段上的 ACK 编号也不增加。
|
||||||
|
|
||||||
|
- 每个段都带有大于等于 0 的窗口信息。
|
||||||
|
|
||||||
|
## 三、实验环境
|
||||||
|
|
||||||
|
- 实验仪器：ThinkPad X230i
|
||||||
|
- 操作系统：Arch GNU/Linux x86\_64
|
||||||
|
- 以太网控制器：Intel Corporation 82575LM Gigabit Network Connection
|
||||||
|
- 网络控制器：Realtek Semiconductor Co., Ltd. RTL8188CE 820.11b/g/n WiFi Adapter
|
||||||
|
- 网络连接：校园网 ECNU-1X
|
||||||
|
|
||||||
|
## 四、实验过程与分析
|
||||||
|
|
||||||
|
1. 捕获
|
||||||
|
|
||||||
|
2. 检查捕获到的内容
|
||||||
|
|
||||||
|
捕获到的内容如图所示：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
3. TCP 段结构
|
||||||
|
|
||||||
|
<table align="center">
|
||||||
|
<tr>
|
||||||
|
<td align="center" colspan='20'>TCP 报头</td>
|
||||||
|
<td align="center">TCP 负载</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td align="center">源端口</td>
|
||||||
|
<td align="center">目标端口</td>
|
||||||
|
<td align="center">序列号</td>
|
||||||
|
<td align="center">确认号</td>
|
||||||
|
<td align="center">报头长度</td>
|
||||||
|
<td align="center">Flags</td>
|
||||||
|
<td align="center">窗口</td>
|
||||||
|
<td align="center">校验和</td>
|
||||||
|
<td align="center">紧急指针</td>
|
||||||
|
<td align="center">Options</td>
|
||||||
|
<td align="center">TCP Payloads</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
<td align="center">4 bytes</td>
|
||||||
|
<td align="center">4 bytes</td>
|
||||||
|
<td align="center">4 bits</td>
|
||||||
|
<td align="center">12 bits</td>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
<td align="center">2 bytes</td>
|
||||||
|
<td align="center">12 bytes</td>
|
||||||
|
<td align="center">Many bytes</td>
|
||||||
|
</tr>
|
||||||
|
</table>
|
||||||
|
|
||||||
|
4. TCP 建立与拆除。
|
||||||
|
|
||||||
|
- 三次握手
|
||||||
|
|
||||||
|
SYN及其之后包的信息如图所示：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
根据所得到的信息画图：
|
||||||
|
|
||||||
|
```mermaid
|
||||||
|
sequenceDiagram
|
||||||
|
autonumber
|
||||||
|
participant Client
|
||||||
|
participant Server
|
||||||
|
Client->>Server: 0th ms, SYN, 序列号: 0
|
||||||
|
Note left of Client: Δ = 96ms
|
||||||
|
Server->>Client: 96th ms, SYN-ACK, 序列号: 0, ACK号: 1
|
||||||
|
Client->>Server: 96th ms, ACK, 序列号: 1, ACK号: 1
|
||||||
|
```
|
||||||
|
|
||||||
|
- 连接选项
|
||||||
|
|
||||||
|
SYN 包具体信息如图所示：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
故可以观察到 SYN 包携带的选项有：
|
||||||
|
|
||||||
|
- Maximum segment size(最大段大小)
|
||||||
|
- SACK permitted(SACK 许可)
|
||||||
|
- Timestamps(时间戳)
|
||||||
|
- NOP(无操作)
|
||||||
|
- Window sacle(窗口比例)
|
||||||
|
|
||||||
|
- FIN/RST 拆除
|
||||||
|
|
||||||
|
FIN及其之后包的信息如图所示：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
根据所得到的信息画图：
|
||||||
|
|
||||||
|
```mermaid
|
||||||
|
sequenceDiagram
|
||||||
|
autonumber
|
||||||
|
participant Client
|
||||||
|
participant Server
|
||||||
|
Client->>Server: 844th ms, FIN-ACK, 序列号: 237, ACK号: 256850
|
||||||
|
Note left of Client: Δ = 45ms
|
||||||
|
Server->>Client: 889th ms, FIN-ACK, 序列号: 256850, ACK号: 238
|
||||||
|
Client->>Server: 889th ms, ACK, 序列号: 238, ACK号: 256851
|
||||||
|
```
|
||||||
|
|
||||||
|
5. TCP 数据传输
|
||||||
|
|
||||||
|
IO 图表如图：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
1. 下载方向的大致数据速率是
|
||||||
|
|
||||||
|
$$
|
||||||
|
\frac{\frac{1}{8}(18+35+13+8+46+23+28+21) packets}{0.1 s} = 240\ packets/s
|
||||||
|
$$
|
||||||
|
|
||||||
|
$$
|
||||||
|
\frac{\frac{1}{8}(185300+401500+149100+91780+527700+263900+321200+226600) bits}{0.1 s} =2708850\ bits/s
|
||||||
|
$$
|
||||||
|
|
||||||
|
2. 查看下载数据包，通过观察包的大小与 TCP 有效负载的大小，计算下载率中有多少百分比是内容？
|
||||||
|
|
||||||
|
$$
|
||||||
|
\frac{1368 bytes}{1434 bytes}=\frac{228}{239} \approx 95.40\%
|
||||||
|
$$
|
||||||
|
|
||||||
|
3. 传输方向的大致数据速率是
|
||||||
|
|
||||||
|
$$
|
||||||
|
\frac{\frac{1}{8}(16+29+13+8+32+10+23+22) packets}{0.1 s} = 191.25\ packets/s
|
||||||
|
$$
|
||||||
|
|
||||||
|
$$
|
||||||
|
\frac{\frac{1}{8}(8448+15310+6864+4224+16990+5280+12140+11620) bits}{0.1 s} =101095\ bits/s
|
||||||
|
$$
|
||||||
|
|
||||||
|
4. 如果最近从服务器接收的 TCP 段的序列号为 x ，那么下一个传输的 TCP 段携带什么 ACK 号？
|
||||||
|
|
||||||
|
**x+TCP 负载字节数**
|
||||||
Binary file not shown.
Binary file not shown.
|
After Width: | Height: | Size: 155 KiB |
Binary file not shown.
File diff suppressed because one or more lines are too long
|
|
@ -0,0 +1,7 @@
|
||||||
|
❯ ./client localhost
|
||||||
|
client1
|
||||||
|
text from client1
|
||||||
|
client1 stop
|
||||||
|
^C
|
||||||
|
./client
|
||||||
|
usage: simplex-talk host
|
||||||
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|
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|
After Width: | Height: | Size: 263 KiB |
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|
After Width: | Height: | Size: 241 KiB |
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|
After Width: | Height: | Size: 174 KiB |
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|
After Width: | Height: | Size: 248 KiB |
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|
After Width: | Height: | Size: 191 KiB |
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|
After Width: | Height: | Size: 202 KiB |
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|
After Width: | Height: | Size: 373 KiB |
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|
After Width: | Height: | Size: 241 KiB |
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|
After Width: | Height: | Size: 211 KiB |
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|
After Width: | Height: | Size: 228 KiB |
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|
After Width: | Height: | Size: 278 KiB |
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|
After Width: | Height: | Size: 239 KiB |
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|
After Width: | Height: | Size: 246 KiB |
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|
After Width: | Height: | Size: 291 KiB |
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|
After Width: | Height: | Size: 245 KiB |
|
|
@ -0,0 +1,286 @@
|
||||||
|
---
|
||||||
|
title: Lab7 - Socket Programming
|
||||||
|
---
|
||||||
|
|
||||||
|
# 华东师范大学软件学院实验报告
|
||||||
|
|
||||||
|
## 一、实验目的
|
||||||
|
|
||||||
|
了解套接字编程相关内容。
|
||||||
|
|
||||||
|
## 二、使用内容与实验步骤
|
||||||
|
|
||||||
|
使用实验手册中所给出的示例代码，并进行相关测试。
|
||||||
|
|
||||||
|
## 三、实验环境
|
||||||
|
|
||||||
|
- 实验仪器1：ThinkPad X230i
|
||||||
|
- 操作系统：6.12.9-arch1-1 x86_64 GNU/Linux
|
||||||
|
- 以太网控制器：Intel Corporation 82575LM Gigabit Network Connection
|
||||||
|
- 网络控制器：Realtek Semiconductor Co., Ltd. RTL8188CE 820.11b/g/n WiFi Adapter
|
||||||
|
|
||||||
|
- 实验仪器2：raspberrypi 4B
|
||||||
|
- 操作系统：6.6.47+rpt-rpi-v8 aarch64 GNU/Linux
|
||||||
|
|
||||||
|
- 网络连接：宿舍 Wifi
|
||||||
|
|
||||||
|
## 四、实验过程与分析
|
||||||
|
|
||||||
|
本地测试记录如下图：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
实验步骤
|
||||||
|
|
||||||
|
1. 启动 Wireshark，根据代码中常量定义，将过滤选项设置为`tcp.port==7701`，对 `Loopback: lo` 进行捕获
|
||||||
|
|
||||||
|
2. 启动服务端
|
||||||
|
|
||||||
|
3. 启动0号客户端,此时 Wireshark 捕获到三次握手包，观察到0号客户端采用44514端口：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
4. 发送文本测试
|
||||||
|
|
||||||
|
1. 0号客户端发送测试文本0（测试短文本)：`text0:hello, world`，服务端显示：`text0:hello, world`，正常发送，Wireshark 捕获到的包信息如下。
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
2. 0号客户端发送测试文本1（测试ACSII可显示字符)：text1: ``!"#\$%&'()*+,-./0123456789:;<=>?`ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_@abcdefghijklmnopqrstuvwxyz{|}~``，服务端显示：text1: ``!"#\$%&'()*+,-./0123456789:;<=>?`ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_@abcdefghijklmnopqrstuvwxyz{|}~``，正常发送，Wireshark 捕获到的包信息如下。
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
3. 0号客户端发送测试文本2（测试tab字符)：`text2:\t \t`，服务端显示：`text2:\t \t`，正常发送，Wireshark 捕获到的包信息如下。
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
可以观察到 tab 以正常形式（ACSII码为9）发出
|
||||||
|
|
||||||
|
4. 0号客户端发送测试文本3（测试中文文本)：`text3:你好，世界`，服务端显示：`text3:你好，世界`，正常发送，Wireshark 捕获到的包信息如下。
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
5. 0号客户端发送测试文本4（测试长文本)：`text4:0123456789abcdef...0123456789abcdef`（共计32774字节），服务端显示：`text4:0123456789abcdef...012345678`（共计4096字节），文本发送不正常，仅发送前 4096 字节，检查 Wireshark ，可以发现0号客户端共发送16个包，前15个包中每个包携带255字节的文本，最后一个包携带16字节的文本，捕获到的第一个与最后一个客户端包信息如下。
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
可以观察到 IP 协议头中 DF 为 1 ，故数据未经 IP 分片，数据的分段发生在 TCP 加工阶段。
|
||||||
|
|
||||||
|
5. 断连测试
|
||||||
|
|
||||||
|
1. 断开0号客户端连接，捕获到由0号客户端发出的结束请求
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
2. 重新恢复0号客户端连接
|
||||||
|
|
||||||
|
3. 断开服务端连接，捕获到由服务端发出的结束请求（FIN），0号客户端发送ACK确认，但未得到服务端的ACK确认，于是0号客户端将在等待2MSL后自动断开连接，捕获到的包信息如下：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
4. 0号客户端发送文本`a text from client`， Wireshark 捕获到的内容如下
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
0号客户端发送了带有 PSH 的信息包，端口收到后优先处理该数据包，由于服务端已经关闭，7701端口空闲，故返回带有RST的数据报。
|
||||||
|
|
||||||
|
5. 0号客户端发送文本`server restart`，按下回车后客户端自动退出，Wireshark 没有捕获到消息
|
||||||
|
|
||||||
|
6. 执行指令`./client localhost`，尝试重新启动客户端，收到报错`simplex-talk: connect: Connection refused`，捕获到的包信息如下
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
0号客户端发送了带有 SYN 的信息包，由于服务端已经关闭，7701端口空闲，故返回带有RST的数据报，0号客户端收到后报告错误并退出
|
||||||
|
|
||||||
|
7. 执行指令`./client`，不指定地址，报错`usage: simplex-talk host`
|
||||||
|
|
||||||
|
6. 多客户端测试
|
||||||
|
|
||||||
|
1. 重新启动服务端
|
||||||
|
2. 启动0号客户端，观察 Wireshark ，可以发现0号客户端使用端口为53092
|
||||||
|
3. 0号客户端发送文本`client0`，服务端显示：`client0`，正常发送。
|
||||||
|
4. 启动1号客户端，观察 Wireshark ，可以发现1号客户端使用端口为43676，Wireshark 捕获包信息如下：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
5. 1号客户端发送文本`client1`，服务端没有显示，但 Wireshark 捕获到信息包。
|
||||||
|
6. 0号客户端发送文本`text from client0`，服务端显示`text from client0`，正常发送。
|
||||||
|
7. 1号客户端发送文本`text from client1`，服务端没有显示，但 Wireshark 捕获到信息包。
|
||||||
|
8. 0号客户端发送文本`client0 stop`，服务端显示`client0 stop`，正常发送。
|
||||||
|
9. 0号客户端断开连接，服务端显示`client1`
|
||||||
|
10. 0号客户端发送文本`client1 stop`，服务端显示`client1 stop`，正常发送。
|
||||||
|
11. 断开服务端连接。
|
||||||
|
|
||||||
|
1 号客户端发送的三个携带文本的信息包如下：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
7. 端口占用测试
|
||||||
|
|
||||||
|
1. 启动服务端，Wireshark 未捕获到内容
|
||||||
|
2. 启动第二个服务端，报错`simplex-talk: bind: Address already in use`，Wireshark 未捕获到内容
|
||||||
|
3. 启动客户端
|
||||||
|
4. 关闭服务端
|
||||||
|
5. 尝试重新启动服务端，报错`simplex-talk: bind: Address already in use`，Wireshark 未捕获到内容
|
||||||
|
6. 客户端退出
|
||||||
|
7. 尝试重新启动服务端，服务端正常运行
|
||||||
|
|
||||||
|
测试截图如下：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
8. 局域网通信测试
|
||||||
|
|
||||||
|
1. 通过 ssh 连接并控制同一局域网下的另一设备
|
||||||
|
|
||||||
|
2. 通过 ftp 上传源代码server.c与client.c
|
||||||
|
|
||||||
|
3. 在 ssh 所控制设备上编译
|
||||||
|
|
||||||
|
4. 启动 Wireshark ，将过滤器设置为`tcp.port == 7701`，对wlan0进行捕获
|
||||||
|
|
||||||
|
5. 在远程主机上执行`./server`，在电脑上执行`./client 192.168.31.135`，成功连接
|
||||||
|
|
||||||
|
6. 在客户端上发送信息，远程服务端成功收到
|
||||||
|
|
||||||
|
7. 交换客户端与服务端，仍能成功通信
|
||||||
|
|
||||||
|
通信记录与 Wireshark 捕获截图如下：
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
## 五、附录
|
||||||
|
|
||||||
|
客户端代码如下：
|
||||||
|
|
||||||
|
```c
|
||||||
|
/* Source: Peterson & Davie (2007), Computer Networks, a Systems Approach,
|
||||||
|
* 4th ed., Morgan Kaufmann, p. 34-35.
|
||||||
|
* Included stdlib.h, string.h, and strings.h so it compiles on Linux.
|
||||||
|
* Changed port from 5432 (postgresql) to 7701 (unassigned).
|
||||||
|
* - JLND Feb 7 2009
|
||||||
|
*/
|
||||||
|
#include <unistd.h>
|
||||||
|
#include <unistd.h>
|
||||||
|
#include <stdlib.h>
|
||||||
|
#include <string.h>
|
||||||
|
#include <strings.h>
|
||||||
|
#include <stdio.h>
|
||||||
|
#include <sys/types.h>
|
||||||
|
#include <sys/socket.h>
|
||||||
|
#include <netinet/in.h>
|
||||||
|
#include <netdb.h>
|
||||||
|
#define SERVER_PORT 7701
|
||||||
|
#define MAX_LINE 256
|
||||||
|
|
||||||
|
int main(int argc, char * argv[])
|
||||||
|
{
|
||||||
|
FILE *fp;
|
||||||
|
struct hostent *hp;
|
||||||
|
struct sockaddr_in sin;
|
||||||
|
char *host;
|
||||||
|
char buf[MAX_LINE];
|
||||||
|
int s;
|
||||||
|
int len;
|
||||||
|
|
||||||
|
if (argc==2) {
|
||||||
|
host = argv[1];
|
||||||
|
}
|
||||||
|
else {
|
||||||
|
fprintf(stderr, "usage: simplex-talk host\n");
|
||||||
|
exit(1);
|
||||||
|
}
|
||||||
|
|
||||||
|
/* translate host name into peer’s IP address */
|
||||||
|
hp = gethostbyname(host);
|
||||||
|
if (!hp) {
|
||||||
|
fprintf(stderr, "simplex-talk: unknown host: %s\n", host);
|
||||||
|
exit(1);
|
||||||
|
}
|
||||||
|
|
||||||
|
/* build address data structure */
|
||||||
|
bzero((char *)&sin, sizeof(sin));
|
||||||
|
sin.sin_family = AF_INET;
|
||||||
|
bcopy(hp->h_addr, (char *)&sin.sin_addr, hp->h_length);
|
||||||
|
sin.sin_port = htons(SERVER_PORT);
|
||||||
|
|
||||||
|
/* active open */
|
||||||
|
if ((s = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
|
||||||
|
perror("simplex-talk: socket");
|
||||||
|
exit(1);
|
||||||
|
}
|
||||||
|
if (connect(s, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
|
||||||
|
perror("simplex-talk: connect");
|
||||||
|
close(s);
|
||||||
|
exit(1);
|
||||||
|
}
|
||||||
|
|
||||||
|
/* main loop: get and send lines of text */
|
||||||
|
while (fgets(buf, sizeof(buf), stdin)) {
|
||||||
|
buf[MAX_LINE-1] = '\0';
|
||||||
|
len = strlen(buf) + 1;
|
||||||
|
send(s, buf, len, 0);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
服务端代码如下：
|
||||||
|
|
||||||
|
```c
|
||||||
|
/* Source: Peterson & Davie (2007), Computer Networks, a Systems Approach,
|
||||||
|
* 4th ed., Morgan Kaufmann, p. 35-36.
|
||||||
|
* Included stdlib.h, string.h, and strings.h so it compiles on Linux.
|
||||||
|
* Changed port from 5432 (postgresql) to 7701 (unassigned).
|
||||||
|
* - JLND Feb 7 2009
|
||||||
|
*/
|
||||||
|
#include <unistd.h>
|
||||||
|
#include <stdlib.h>
|
||||||
|
#include <string.h>
|
||||||
|
#include <strings.h>
|
||||||
|
#include <stdio.h>
|
||||||
|
#include <sys/types.h>
|
||||||
|
#include <sys/socket.h>
|
||||||
|
#include <netinet/in.h>
|
||||||
|
#include <netdb.h>
|
||||||
|
#define SERVER_PORT 7701
|
||||||
|
#define MAX_PENDING 5
|
||||||
|
#define MAX_LINE 256
|
||||||
|
|
||||||
|
int main()
|
||||||
|
{
|
||||||
|
struct sockaddr_in sin;
|
||||||
|
char buf[MAX_LINE];
|
||||||
|
int len;
|
||||||
|
int s, new_s;
|
||||||
|
|
||||||
|
/* build address data structure */
|
||||||
|
bzero((char *)&sin, sizeof(sin));
|
||||||
|
sin.sin_family = AF_INET;
|
||||||
|
sin.sin_addr.s_addr = INADDR_ANY;
|
||||||
|
sin.sin_port = htons(SERVER_PORT);
|
||||||
|
|
||||||
|
/* setup passive open */
|
||||||
|
if ((s = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
|
||||||
|
perror("simplex-talk: socket");
|
||||||
|
exit(1);
|
||||||
|
}
|
||||||
|
if ((bind(s, (struct sockaddr *)&sin, sizeof(sin))) < 0) {
|
||||||
|
perror("simplex-talk: bind");
|
||||||
|
exit(1);
|
||||||
|
}
|
||||||
|
listen(s, MAX_PENDING);
|
||||||
|
|
||||||
|
/* wait for connection, then receive and print text */
|
||||||
|
while(1) {
|
||||||
|
if ((new_s = accept(s, (struct sockaddr *)&sin, &len)) < 0) {
|
||||||
|
perror("simplex-talk: accept");
|
||||||
|
exit(1);
|
||||||
|
}
|
||||||
|
while (len = recv(new_s, buf, sizeof(buf), 0))
|
||||||
|
fputs(buf, stdout);
|
||||||
|
close(new_s);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
```
|
||||||
Binary file not shown.
|
|
@ -0,0 +1,17 @@
|
||||||
|
❯ ./server
|
||||||
|
text0:hello, world
|
||||||
|
text1: !"#$%&'()*+,-./0123456789:;<=>?`ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_@abcdefghijklmnopqrstuvwxyz{|}~
|
||||||
|
text2:\t \t
|
||||||
|
text3:你好，世界
|
||||||
|
text4:0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef012345678
|
||||||
|
client0 stop
|
||||||
|
client0 restart
|
||||||
|
server stop
|
||||||
|
^C
|
||||||
|
❯ ./server
|
||||||
|
client0
|
||||||
|
text from client0
|
||||||
|
client0 stop
|
||||||
|
client1
|
||||||
|
client1 stop
|
||||||
|
^C
|
||||||
File diff suppressed because one or more lines are too long
Loading…
Reference in New Issue