Python, fill in code are marked with #FillInStart and #FillInEnd import socket import sys import os # Since the server might send the HTML across more than one # send, we should try multiple recv calls to receive all data def recvall(sock): BUFFER_SIZE = 4096 # 4 KiB data = b"" while True: part = sock.recv(BUFFER_SIZE) data += part # Keep receiving only until the received data "ended" in last recv if len(part) < BUFFER_SIZE: break return data # Create a server socket, bind it to a port and start listening listener = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # FillInStart # FillInEnd print('Ready to serve...') while True: # accept a connection from the client side and decode the message/request clientSide, addr = listener.accept() message = #FillInStart #FillInEnd # for now, lets ignore all the requests that are not GET # the remaining requests will just be discarded and the client # will receive no response for those requests if not message.startswith("GET"): continue # extract the URL, domain, method, path from the request request_method = message.split()[0] requested_url = message.split()[1] domain = requested_url.split("/", 3)[2] path = requested_url.split("/", 3)[3] # if the path ends in / then we can name it as index.html since # is usually the case across the web if path == "": path = "index.html" print("request method: {}, requested URL: {} -> domain: {}, path: {}".format(request_method, requested_url, domain, path)) # create the directory structure similar to how the paths # are defined within the URL. So, the parent folder will be the # domain you are visiting and the path will be converted into # subdirectories within the parent folder for intuitive navigation file_path = "./{}/{}".format(domain, path) file_exists = os.path.exists(file_path) if file_exists: # if the file exists, we can just read it and send it print("file was found in the local cache at the proxy") f = open(file_path, "rb") outputdata = f.read() else: # otherwise, we need to make the request to the remote server # to retrieve the file and send it to client while also saving # it locally for future visits print("file was NOT found in the local cache at the proxy") print("requesting from server...") # the GET request is made on HTTP/1.0 so that we don't need to # deal with gzip compression and the response handling is fairly # straightforward GET_request = "" GET_request += "GET {} HTTP/1.0\r\n".format(requested_url) GET_request += "Host: {}\r\n\r\n".format(domain) print(GET_request) # we open the socket to the server and make the request at port 80 # FillInStart # FillInEnd # using the port you have created above to send the GET request serverSide.send(GET_request.encode()) # receive the response using recvall in case the response takes more # than one send by the server to send GET_response = recvall(serverSide) print("R: {}".format(GET_response)) # we create the directory and subdirectories in case they don't # don't exist already and save the response as a.

1. Python, fill in code are marked with #FillInStart and #FillInEnd
import socket
import sys
import os
# Since the server might send the HTML across more than one
# send, we should try multiple recv calls to receive all data
def recvall(sock):
BUFFER_SIZE = 4096 # 4 KiB
data = b""
while True:
part = sock.recv(BUFFER_SIZE)
data += part
# Keep receiving only until the received data "ended" in last recv
if len(part) < BUFFER_SIZE:
break
return data
# Create a server socket, bind it to a port and start listening
listener = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# FillInStart
# FillInEnd
print('Ready to serve...')
while True:
# accept a connection from the client side and decode the message/request
clientSide, addr = listener.accept()
message = #FillInStart #FillInEnd
# for now, lets ignore all the requests that are not GET
# the remaining requests will just be discarded and the client
# will receive no response for those requests
if not message.startswith("GET"):
continue
# extract the URL, domain, method, path from the request
request_method = message.split()[0]
requested_url = message.split()[1]
domain = requested_url.split("/", 3)[2]
path = requested_url.split("/", 3)[3]

2. # if the path ends in / then we can name it as index.html since
# is usually the case across the web
if path == "":
path = "index.html"
print("request method: {}, requested URL: {} -> domain: {}, path:
{}".format(request_method, requested_url, domain, path))
# create the directory structure similar to how the paths
# are defined within the URL. So, the parent folder will be the
# domain you are visiting and the path will be converted into
# subdirectories within the parent folder for intuitive navigation
file_path = "./{}/{}".format(domain, path)
file_exists = os.path.exists(file_path)
if file_exists:
# if the file exists, we can just read it and send it
print("file was found in the local cache at the proxy")
f = open(file_path, "rb")
outputdata = f.read()
else:
# otherwise, we need to make the request to the remote server
# to retrieve the file and send it to client while also saving
# it locally for future visits
print("file was NOT found in the local cache at the proxy")
print("requesting from server...")
# the GET request is made on HTTP/1.0 so that we don't need to
# deal with gzip compression and the response handling is fairly
# straightforward
GET_request = ""
GET_request += "GET {} HTTP/1.0rn".format(requested_url)
GET_request += "Host: {}rnrn".format(domain)
print(GET_request)
# we open the socket to the server and make the request at port 80
# FillInStart
# FillInEnd
# using the port you have created above to send the GET request
serverSide.send(GET_request.encode())

3. # receive the response using recvall in case the response takes more
# than one send by the server to send
GET_response = recvall(serverSide)
print("R: {}".format(GET_response))
# we create the directory and subdirectories in case they don't
# don't exist already and save the response as a file there
file_dir = file_path.rsplit("/", 1)[0]
if not os.path.exists(file_dir):
os.makedirs(file_dir)
with open(file_path, "wb") as f:
f.write(GET_response)
# we are also going to send this response to the client
outputdata = GET_response
# send the outputdata (GET response) back to the client
# FillInStart
# FillInEnd
print("data sent")
listener.close()