can you fill in where it says #Fill in start please? thanks from socket import *

Question

can you fill in where it says #Fill in start please? thanks

from socket import *
import sys
if len(sys.argv) <= 1:
print 'Usage : "python ProxyServer.py server_ip" [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 ")
tcpCliSock.send("Content-Type:text/html ")
# 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 ")
# 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.

Explanation / Answer

a very simple proxy example that can be connected to and will then itself try to connect to the address passed to it." That is practically the definition of an HTTP proxy. There's a really simple proxy example here: http://effbot.org/librarybook/simplehttpserver.htm The core of it is just 3 lines: class Proxy(SimpleHTTPServer.SimpleHTTPRequestHandler): def do_GET(self): self.copyfile(urllib.urlopen(self.path), self.wfile) So it's a SimpleHTTPRequestHandler that, in response to a GET request, opens the URL in the path (a request to a proxy typically looks like "GET http://example.com/", not like "GET /index.html"). It then just copies whatever it can read from that URL to the response.

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