作业 - Python 代理服务器

对于编程练习（摘自《计算机网络：自上而下的方法》（第 6 版）作者：Kurose 和 Ross），我们正在尝试用 python 开发一个简单的代理服务器。

我们得到了以下代码，无论它在哪里#Fill in start. ... #Fill in end.这就是我们需要编写代码的地方。我的具体问题和尝试将在这个原始片段下方。

我们需要使用以下命令启动 python 服务器：python proxyserver.py [server_ip]然后导航到localhost:8888/google.com当我们完成后它应该可以工作。

from socket import *
import sys
if len(sys.argv) <= 1:
  print 'Usage : "python ProxyServer.py server_ip"\n[server_ip : It is the IP Address Of Proxy Server'
  sys.exit(2)

# 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 client
  print '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 message print message.split()[1]
  filename = message.split()[1].partition("/")[2] print filename
  fileExist = "false"
  filetouse = "/" + filename
  print filetouse
  try:
    # Check wether the file exist in the cache
    f = open(filetouse[1:], "r")
    outputdata = f.readlines()
    fileExist = "true"

    # ProxyServer finds a cache hit and generates a response message     
    tcpCliSock.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 cache
except IOError:
  if fileExist == "false":
    # Create a socket on the proxyserver
    c = # 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 client
        fileobj = 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 cache
        tmpFile = 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.

其中说：

# Create a socket on the proxyserver
c = # Fill in start. # Fill in end. 

I tried:

c = socket(AF_INET, SOCK_STREAM)

这似乎是创建套接字的方式，然后为了连接到主机的端口 80，我有：

c.connect((hostn, 80))

Here, hostn是正确的google.com根据我拥有的一些当地打印报表。我要填写的下一部分说#Read response into buffer但我不太明白那是什么意思。我认为这与fileobj这是在上面创建的。

预先感谢，如果我遗漏了任何应该添加的内容，请告诉我。

UPDATE

我当前的代码可以在这里找到，看看我一直在尝试什么：

https://github.com/ardavis/Computer-Networks/blob/master/Lab%203/ProxyServer.py https://github.com/ardavis/Computer-Networks/blob/master/Lab%203/ProxyServer.py

这似乎是我潜在的解决方案。作业中的 pdf 提到我最后需要做一些事情，但不确定它是什么。但缓存和代理似乎与此相关。我希望它对其他人有帮助。

from socket import *
import sys

if len(sys.argv) <= 1:
    print 'Usage: "python ProxyServer.py server_ip"\n[server_ip : It is the IP Address of the Proxy Server'
    sys.exit(2)

# Create a server socket, bind it to a port and start listening
tcpSerPort = 8888
tcpSerSock = socket(AF_INET, SOCK_STREAM)

# Prepare a server socket
tcpSerSock.bind(('', tcpSerPort))
tcpSerSock.listen(5)

while True:
    # Start receiving data from the client
    print 'Ready to serve...'
    tcpCliSock, addr = tcpSerSock.accept()
    print 'Received a connection from: ', addr
    message = tcpCliSock.recv(1024)

    # Extract the filename from the given message
    print message.split()[1]
    filename = message.split()[1].partition("/")[2]
    fileExist = "false"
    filetouse = "/" + filename
    try:
        # Check whether the file exists in the cache
        f = open(filetouse[1:], "r")
        outputdata = f.readlines()
        fileExist = "true"
        print 'File Exists!'

        # ProxyServer finds a cache hit and generates a response message
        tcpCliSock.send("HTTP/1.0 200 OK\r\n")
        tcpCliSock.send("Content-Type:text/html\r\n")

        # Send the content of the requested file to the client
        for i in range(0, len(outputdata)):
            tcpCliSock.send(outputdata[i])
        print 'Read from cache'

        # Error handling for file not found in cache
    except IOError:
        print 'File Exist: ', fileExist
        if fileExist == "false":
            # Create a socket on the proxyserver
            print 'Creating socket on proxyserver'
            c = socket(AF_INET, SOCK_STREAM)

            hostn = filename.replace("www.", "", 1)
            print 'Host Name: ', hostn
            try:
                # Connect to the socket to port 80
                c.connect((hostn, 80))
                print 'Socket connected to port 80 of the host'

                # Create a temporary file on this socket and ask port 80
                # for the file requested by the client 
                fileobj = c.makefile('r', 0)
                fileobj.write("GET " + "http://" + filename + " HTTP/1.0\n\n")

                # Read the response into buffer
                buff = fileobj.readlines() 

                # 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 cache
                tmpFile = open("./" + filename, "wb")
                for i in range(0, len(buff)):
                    tmpFile.write(buff[i])
                    tcpCliSock.send(buff[i])

            except:
                print 'Illegal request'

        else:
            # HTTP response message for file not found
            # Do stuff here
            print 'File Not Found...Stupid Andy'
            a = 2
    # Close the socket and the server sockets
    tcpCliSock.close()

# Do stuff here