《计算机网络自顶向下》Socket Lab4 HTTP Web Proxy Server_综合

文章目录

- 感谢相关代码链接提供细节出错思路
- 前引
- Lab4 HTTP Web Proxy Server
- - Lab4 文档查阅
  - 服务器框架代码
  - 注意事项（易错点）
  - 修改完的核心代码
  - Lab4 建议Lab实验成果
  - - 直连链接
    - 增加服务器代理
    - 打开服务器代理（进行访问进行缓存）
    - 打开服务器代理（进行访问已缓存）

感谢相关代码链接提供细节出错思路

Computer-Networking-A-Top-Down-Approach-NOTES GitHub 套接字编程作业 + Wireshark实验

前引

说实话这个Lab 昨晚拿到手的时候我都觉得还不困难但为什么直到今天下午的六点钟（虽然睡了一上午+去核酸检测耽误了很久）才做出来根本就是刚开始有思路却对全局的实现没有一个清晰的认识以及一些细节的把控导致错误频出

趁刚刚才把Lab做出来我还是想一点点抽丝剥解的把这个Lab的实现流程给写出来吧优质的代码在上面我已经提供链接了之后的实验如果有些地方有问题的话大家没思路可以去看看上面的代码还是很真心感谢上面的代码在一些地方我看了才得以矫正不然的话- - 不知道那些细节又要耽误多久

Lab4 HTTP Web Proxy Server

Lab4 文档查阅

方便大家下载相关文档下面是下载链接中文翻译找到Python3 socket即可
Pearson Computer Networking: a Top-Down Approach, 8th Edition

看看中文翻译由于书本上的我们任务时强调多线程调度而实验中的是强调我们把缓存给整明白了我们大致浏览了一下就可以先把思路给理一下

1、我们需要设置代理服务器我们所有的网页访问都经由代理服务器
2、我们主要是要把缓存给弄好即如果访问过的文件即直接返回即可（当然这是很简单的缓存就不涉及修改时间那些的如果有缓存的话直接返回即可）
在这里插入图片描述

服务器框架代码

from socket import *
import sys
# Create a server socket, bind it to a port and start listening
tcpSerSock = socket(AF_INET, SOCK_STREAM)
# Fill in start.
# Fill in end.
while 1:# Strat receiving data from the clientprint('Ready to serve...')tcpCliSock, addr = tcpSerSock.accept()print('Received a connection from:', addr)message = # Fill in start. # Fill in end.print(message)# Extract the filename from the given messageprint(message.split()[1])filename = message.split()[1].partition("/")[2]print(filename)fileExist = "false"filetouse = "/" + filenameprint(filetouse)try:# Check wether the file exist in the cachef = open(filetouse[1:], "r") outputdata = f.readlines() fileExist = "true"# ProxyServer finds a cache hit and generates a response messagetcpCliSock.send("HTTP/1.0 200 OK\r\n") tcpCliSock.send("Content-Type:text/html\r\n")# Fill in start.# Fill in end.print('Read from cache') # Error handling for file not found in cacheexcept IOError:if fileExist == "false": # Create a socket on the proxyserverc = # Fill in start. # Fill in end.hostn = filename.replace("www.","",1) print(hostn) try:# Connect to the socket to port 80# Fill in start.# Fill in end.# Create a temporary file on this socket and ask port 80 for the file requested by the clientfileobj = c.makefile('r', 0) fileobj.write("GET "+"http://" + filename + " HTTP/1.0\n\n") # Read the response into buffer# Fill in start.# Fill in end.# Create a new file in the cache for the requested file. # Also send the response in the buffer to client socket and the corresponding file in the cachetmpFile = open("./" + filename,"wb") # Fill in start.# Fill in end.except:print("Illegal request") else:# HTTP response message for file not found# Fill in start.# Fill in end.# Close the client and the server sockets tcpCliSock.close() # Fill in start.# Fill in end.

注意事项（易错点）

其实这个Lab你说难吧又不难思路很清晰但是呢一行行代码写下来还是很容易出错的所以建议写一步检查一步

下面一些点是我写的时候出错检查了很久的地方
1、windows中存储/r/n 再读取时会导致第一行出错并且会多打一行
所以我们在存入的时候需要把/r/n给替换成/r 如果不这样处理返回时第一条HTTP/1.1 200 OK就被吞了
2、文件打开处理同一个文件打开用同一个变量我反正用其他变量就会报错不知道为什么
3、文字处理数目尽量大一点我设置为1024的时候会报错然后就设置成4096了
4、缓存路径存储记得把文件的/替换成_或者其他符号因为这个在路径中寻找时或者创建时会变成下一层路径寻址就会出错

其他的就是路径设置了和一些python语法函数问题了大家注意一下即可
当然原版的框架我也做了很多修改

修改完的核心代码

下面就直接改代码了如果大家自己的代码哪里出问题了可以看一下下面的代码作为参照

from socket import *
import sys
# Create a server socket, bind it to a port and start listening
tcpSerSock = socket(AF_INET, SOCK_STREAM)
tcpSerSock.bind(('0.0.0.0',2333))
tcpSerSock.listen(5)
while 1:# Strat receiving data from the clientprint('Ready to serve...')tcpCliSock, addr = tcpSerSock.accept()print('Received a connection from:', addr)message = tcpCliSock.recv(4096).decode()allpath = message.split()[1].partition("//")[2]requestWeb = allpath.partition('/')[0]filename = allpath.partition("/")[2].replace('/','_')fileExist = Falsefilepath  = "D:/Love6 html cache/" + requestWeb + '_' + filename# Check whether the file exist in the cachetry:f = open(filepath, "r")print("file Exist")outputdata = f.read()fileExist = True# ProxyServer finds a cache hit and generates a response messagetcpCliSock.send(outputdata.encode())print('Read from cache')f.close()# Error handling for file not found in cacheexcept IOError:if fileExist == False:# Create a socket on the proxyserverprint("file Not Exist"+ '___' + requestWeb)c = socket(AF_INET, SOCK_STREAM)requestPort = 80try:# Connect to the socket to port 80c.connect((requestWeb,requestPort))c.send(message.encode())retSentence = c.recv(4096).decode()# Create a new file in the cache for the requested file.# Also send the response in the buffer to client socket and the corresponding file in the cachetcpCliSock.send(retSentence.encode())print(filepath)f = open(filepath, "w")f.write(retSentence.replace('\r\n', '\n'))f.close()except:print("Illegal request")c.close()else:# HTTP response message for file not foundtcpCliSock.send("HTTP/1.0 404 Not Found\r\n".encode())tcpCliSock.send("\r\n".encode())tcpCliSock.send("404 Not Found Cant Find such file " + filename +"\r\n".encode())# Close the client and the server socketstcpCliSock.close()
tcpSerSock.close()