# 实验 ## telnet 与 HTTP 实验 `telnet`命令可以手动编辑和发送报文，Linux 和 Windows 都可以使用找了一个远程 Linux 服务器进行实验系统为 CentOS，想要安装`telnet`命令，root 使用命令： ```shell yum install telnet ``` 这里用书上的例子 ``` [root@qmmms ~]# telnet gaia.cs.umass.edu 80 Trying 128.119.245.12... Connected to gaia.cs.umass.edu. Escape character is '^]'. GET /kurose_ross/interactive/index.php HTTP/1.1 Host: gaia.cs.umass.edu ``` 注意最后按两下回车结束，得到结果： ``` HTTP/1.1 200 OK Date: Fri, 30 Sep 2022 07:11:13 GMT Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/7.4.30 mod_perl/2.0.11 Perl/v5.16.3 X-Powered-By: PHP/7.4.30 Set-Cookie: DevMode=0 Transfer-Encoding: chunked Content-Type: text/html; charset=UTF-8 361c [...省略...] ``` > 补充：使用Chrome浏览器，进入开发者模式，进入网络，随便选一个请求，可以看到报文 ## telnet 与 SMTP 实验 SMTP 是电子邮件使用的应用层协议，同样可以使用`telnet`命令手动模拟发邮件一端可以使用远程 Linux 主机使用 SMTP 协议的邮件服务器比较难找，试了试，学校(DUT)邮箱可以用 **用户端需要手动键入的信息有：** ``` HELO xxx.xxx.xxx.x #我的远程主机 MAIL FROM: <用户@xxx.xxx.xxx.x> #发送方 RCPT TO: <用户@对方地址> #收件方 DATA #开始输入正文 . #以单行.作为正文结束 QUIT #结束连接 ``` **全部实验过程：** ``` [user1@qmmms ~]$ telnet mail.dlut.edu.cn 25 Trying 202.118.66.82... Connected to mail.dlut.edu.cn. Escape character is '^]'. 220 mail.dlut.edu.cn ESMTP mail service ready HELO xxx.xxx.xxx.x 250 OK MAIL FROM: 250 Mail OK RCPT TO: 250 Mail OK DATA 354 End data with . hello from linux . 250 Mail OK queued as UEJ2ygBnb+8toTZjKwx_CA--.36240S2 QUIT 221 Bye Connection closed by foreign host. ``` 最后在学校邮箱的垃圾邮件里面找到了这个邮件 > 补充：就现在而言（2022），大部分电子邮件功能支持都以网页版形式呈现，发邮件可以使用 SMTP 协议，查收邮件 HTTP 协议（通过网页） ## telnet 与 POP3 实验 POP3协议，用于接收邮件，同样可以使用`telnet`命令手动模拟 **用户端需要手动键入的信息有：** ``` user 账号 pass 密码 list #列出所有邮件 retr 数字 #查看数字标识的邮件 dele 数字 #删除数字标识的邮件 quit #退出 ``` **全部实验过程：** ``` [user1@qmmms ~]$ telnet mail.dlut.edu.cn 110 Trying 202.118.66.82... Connected to mail.dlut.edu.cn. Escape character is '^]'. +OK Welcome to coremail Mail Pop3 Server (dlut.edu.cns[627644c969381353b51c9657b72568a4s]) user xxxxxxxxxx@mail.dlut.edu.cn +OK core mail pass xxxxxxxxxx +OK 4 message(s) [1151199 byte(s)] list +OK 4 1151199 1 398270 2 741119 3 1682 4 10128 . retr 3 +OK 1682 octets Received: from xxxxxxxxx (unknown [xxxxxxxxx]) by mx1 (Coremail) with SMTP id UEJ2ygBnb+8toTZjKwx_CA--.36240S2; Fri, 30 Sep 2022 15:56:40 +0800 (CST) hello from linux X-CM-TRANSID:UEJ2ygBnb+8toTZjKwx_CA--.36240S2 Message-Id:<6336A15F.04A767.07381@dlut.edu.cn> Authentication-Results: mx1; spf=none smtp.mail=xxx@xxxxxx; X-Coremail-Antispam: 1UD129KBjDUn29KB7ZKAUJUUUUU529EdanIXcx71UUUUU7v73 VFW2AGmfu7jjvjm3AaLaJ3UjIYCTnIWjp_UUUrS7k0a2IF6F4UM7kC6x804xWl14x267AK xVWUJVW8JwAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26r1j6r1xM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r1j 6r4UM28EF7xvwVC2z280aVAFwI0_Jr0_Gr1l84ACjcxK6I8E87Iv6xkF7I0E14v26r1j6r 4UM2vYz4IE57IF64kE628EF7xvwwAS0I0E0xvYzxvE52x082IY62kv0487M2AExVAIFx02 aVAFz4v204v7Mc8Ir4CE8sxKj4xv1VAv77x28xyl52xGzVA2a4k0FcxF6cIjj282cryl5I 8CrVACY4xI64kE6c02F40Ex7xfMcIj64x0Y40En7xvr7AKxVWUJVW8JwAv7VC0I7IYx2IY 67AKxVWUtVWrXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0Y4 8IcVAKI48JM4x0aVACjI8F5VA0II8E6IAqYI8I648v4I1lw4AK0VCY07AIYIkI8VC2zVAC 3wAKzVAC0xCFj2AI6cx7M4kE6I8I3I0E14AKx2xKxVC2ax8xMx02cVCv0xWlc7CjxVAKzI 0EY4vE52x082I5MxkI7II2jI8vz4vEwIxGrwCYIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCY IxAIcVC0I7IYx2IY6xkF7I0E14v26r1j6r4UMxvI42IY6I8E87Iv67AKxVWUJVW8JwCYIx AIcVC2z280aVCY1x0267AKxVWUJVW8JwCF04k20xvY0x0EwIxGrwCF04k20xvEw4C26cxK 6c8Ij28IcwCFw20E84ACjcxK64kEx2IqYxC7MxCjnVAKz4kxMxC20s026xCaFVCjc4AY6r 1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_Jr0_Jr4lx4CE17CE b7AF67AKxVWUJVWUXwCI42IY6xAIw20EY4v20xvaj40_Zr0_Wr1UYxBIdaVFxhVjvjDU0x ZFpf9x07b6AwxUUUUU= Date: Fri, 30 Sep 2022 15:57:19 +0800 (CST) From: xxx@xxxxxx . quit +OK core mail Connection closed by foreign host. ``` ## DNS实验使用远程 LInux 主机 ### 基本介绍 bind是linux系统下的一个DNS服务程序 bind-utils是bind软件提供的一组DNS工具包,可以进行域名解析和DNS调试工作主要有：dig,host,nslookup,nsupdate ### 安装工具包 Cent OS 使用命令（root用户） ```shell sudo yum install bind-utils ``` ### 使用 nslookup用于查询DNS的记录，输入一个主机名并发现相应的IP地址 ``` [user1@qmmms ~]$ nslookup www.baidu.com Server: 100.125.1.250 Address: 100.125.1.250#53 Non-authoritative answer: www.baidu.com canonical name = www.a.shifen.com. Name: www.a.shifen.com Address: 110.242.68.4 Name: www.a.shifen.com Address: 110.242.68.3 ``` ``` [user1@qmmms ~]$ host www.baidu.com www.baidu.com is an alias for www.a.shifen.com. www.a.shifen.com has address 110.242.68.3 www.a.shifen.com has address 110.242.68.4 ``` ``` [user1@qmmms ~]$ dig www.baidu.com ; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el7_9.9 <<>> www.baidu.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 38365 ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;www.baidu.com. IN A ;; ANSWER SECTION: www.baidu.com. 399 IN CNAME www.a.shifen.com. www.a.shifen.com. 21 IN A 110.242.68.3 www.a.shifen.com. 21 IN A 110.242.68.4 ;; Query time: 0 msec ;; SERVER: 100.125.1.250#53(100.125.1.250) ;; WHEN: Mon Oct 03 12:54:30 CST 2022 ;; MSG SIZE rcvd: 101 ``` ## UDP套接字编程 ### 目标 1. 在本地客户端输入一段字符串 2. 发送给服务器 3. 服务器把字符串改为全大写 4. 发送给本地客户端 5. 本地客户端显示修改过的字符串 ### 准备当然要两台电脑，或者虚拟机，或者租一个远程服务器作者租了一个远程服务器，Linux 系统，提前把 python3 之类的环境配置好如果远程服务器开了防火墙，记得把相关端口允许放行，或者短暂关闭防火墙 ### 客户端代码 > code 文件夹下 UDPClient.py ```python from socket import * serverName = 'xxx.xxx.xxx.xxx' # 把远程服务器的ip或主机名填这里 serverPort = 12000 clientSocket = socket(AF_INET, SOCK_DGRAM) # 指示网络选择IPv4和UDP message = input("Input lowercase sentence: ") clientSocket.sendto(message.encode(), (serverName, serverPort)) # 发送信息 print("have sent message \"", message, "\" to", serverName) modifiedMessage, serverAddress = clientSocket.recvfrom(2048) # 接收信息，2048表示缓存长度 print(modifiedMessage.decode()) clientSocket.close() ``` ### 服务器端代码 > code 文件夹下 UDPServer.py ```python from socket import * serverPort = 12000 serverSocket = socket(AF_INET, SOCK_DGRAM) # 指示网络选择IPv4和UDP serverSocket.bind(('', serverPort)) # 绑定本机ip和端口 print("The server is ready to receive") while True: message, clientAddress = serverSocket.recvfrom(2048) # 从客户端接收信息，2048表示缓存长度 print("receive from", clientAddress, ": ", message.decode()) modifiedMessage = message.decode().upper() # 转大写 print("have sent message back: ", modifiedMessage) serverSocket.sendto(modifiedMessage.encode(), clientAddress) # 发给客户端 ``` ### 运行实例当然，服务器端的代码要先开始运行，然后打开客户端输入 **客户端：** ``` Input lowercase sentence: hello world have sent message " hello world " to xxx.xxx.xxx.xxx HELLO WORLD ``` **服务器端：** ``` The server is ready to receive receive from ('xxx.xxx.xxx.xxx', xxxx) : hello world have sent message back: HELLO WORLD ``` ## TCP套接字编程 ### 目标 1. 在本地客户端输入一段字符串 2. 发送给服务器 3. 服务器把字符串改为全大写 4. 发送给本地客户端 5. 本地客户端显示修改过的字符串 ### 客户端代码 > code 文件夹下 TCPClient.py ```python from socket import * serverName = 'xxx.xxx.xxx.xxx' # 把远程服务器的ip或主机名填这里 serverPort = 12000 clientSocket = socket(AF_INET, SOCK_STREAM) # 指示网络选择IPv4和TCP clientSocket.connect((serverName, serverPort)) # TCP 需要先建立连接 message = input("Input lowercase sentence: ") clientSocket.send(message.encode()) print("have sent message \"", message, "\" to", serverName) modifiedMessage = clientSocket.recv(2048) print(modifiedMessage.decode()) clientSocket.close() ``` ### 服务器端代码 > code 文件夹下 TCPServer.py ```python from socket import * serverPort = 12000 serverSocket = socket(AF_INET, SOCK_STREAM) # 指示网络选择IPv4和TCP serverSocket.bind(('', serverPort)) # 绑定本机ip和端口 serverSocket.listen(1) # 等待某个用户来连接 print("The server is ready to receive") while True: connectionSocket, addr = serverSocket.accept() # 接收连接请求，创建连接 message = connectionSocket.recv(2048).decode() # 从客户端接收信息，2048表示缓存 print("receive from", addr, ": ", message) modifiedMessage = message.upper() connectionSocket.send(modifiedMessage.encode()) # 发给客户端 print("have sent message back: ", modifiedMessage) ``` ### 运行实例 **客户端：** ``` Input lowercase sentence: hello tcp have sent message " hello tcp " to xxx.xxx.xxx.xxx HELLO TCP ``` **服务器端：** ``` The server is ready to receive receive from ('xxx.xxx.xxx.xxx', 6460) : hello tcp have sent message back: HELLO TCP ``` ## WebServer套接字编程作业 ### 目标实现一个 Web 服务器，可以在浏览器上访问 ### 代码 > code 文件夹下 WebServer.py ```python from socket import * serverSocket = socket(AF_INET, SOCK_STREAM) serverSocket.bind(('', 80)) # http 默认使用 80 端口 serverSocket.listen(1) # 最大连接数为1 while True: # Establish the connection print('Ready to serve...') connectionSocket, addr = serverSocket.accept() try: message = connectionSocket.recv(2048) filename = message.split()[1] f = open(filename[1:]) outputdata = f.read() # Send one HTTP header line into socket header = ' HTTP/1.1 200 OK\nConnection: close\nContent-Type: text/html\nContent-Length: %d\n\n' % ( len(outputdata)) connectionSocket.send(header.encode()) # Send the content of the requested file to the client for i in range(0, len(outputdata)): connectionSocket.send(outputdata[i].encode()) connectionSocket.send("\r\n".encode()) connectionSocket.close() except IOError: # Send response message for file not found header = ' HTTP/1.1 404 Found' connectionSocket.send(header.encode()) # Close client socket connectionSocket.close() ``` 为了传输具体的 html 网页，再编写一个简单 html 文件 > code 文件夹下 HelloWorld.html ```html

Hello World!

``` ### 部署将两个文件都放在远程服务器上，运行 WebServer.py --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://qmmms.gitbook.io/note/computer_network/qms08-shi-yan.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.