Web服务器的Python套接字编程

Question

I have created a proxy server that receives requests, searches for the requested file in its cache. If available it returns the cached file. If file is not available then it will ask the actual server, gets it, stores it in the cache and returns the file to the client.

Following is the code:

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)
tcpSerSock.bind((sys.argv[1], 8888))
tcpSerSock.listen(100)

while 1:
    # Strat receiving data from the client
    print 'Ready to serve...'
    tcpCliSock, addr = tcpSerSock.accept()
    print 'Received a connection from:', addr
    message = tcpCliSock.recv(1024)
    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")
        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:
        if fileExist == "false": 
            # Create a socket on the proxyserver
            c = socket(AF_INET, SOCK_STREAM)            
            hostn = filename.replace("www.","",1)         
            print hostn                                   
            try:
                # Connect to the socket to port 80
                c.connect((hostn, 80))
                # 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 line in buff:                                                     
                    tmpFile.write(line);                                               
                    tcpCliSock.send(line);
            except:
                print "Illegal request"                                               
        else:
            # HTTP response message for file not found
            tcpCliSock.send("HTTP/1.0 404 sendErrorErrorError\r\n")                             
            tcpCliSock.send("Content-Type:text/html\r\n")
            tcpCliSock.send("\r\n")
    # Close the client and the server sockets    
    tcpCliSock.close() 
  tcpSerSock.close()

But for every file I request I only get an "illegal request" message printed. There seems to be an issue that the proxy server actually is not able to retrieve the requested file by the client. Can someone tell me where I can improve the code. This is the first time I am coding in Python so please mention any minor errors.

Answer 1

Your request is illegal. For normal http servers, GET must not contain a URL, but only the path. The rest of your proxy contains also many errors. You probably want to use sendall everywhere you use send. recv can receive less that one message, so you have to handle this case also. Why do you use the strings "true" and "false" instead of True and False? There is a security hole, as you can read any file on your computer through your proxy. Reading binary files won't work. You don't close opened files.