Python3 e-learning case 4: writing web proxy

itread01 2020-11-06 01:17:47
python3 python e-learning learning case


Please go to Baidu Encyclopedia for the definition and function of proxy server ~

1. Web Proxy How to realize it

This is based on the previous article “ Write Web Server” It's written , The main logic is shown in the figure below :

 

  What we're going to write is the middle Web Proxy part , When the client to Web Proxy Send a request for access to a web site (Request) When ,Web Proxy You will first check whether you have the requested file , If there is, go straight back to (Response), If not ,Web Proxy It's like Web Server( The server to access the web address ) Send a request to get the target file , And then to Client return .

2. Web Proxy Use

First , When we visit a website, in order to visit through proxy, we can't simply open the browser and enter the URL to visit ( That would be Client Direct to Web Server Transmit Reuest 了 ), Here you can download a file called Wget Tools for , This is for Web Proxy It's like jdk For Java The same thing ( Of course, there may be other tools that can access the proxy server first , There is no discussion about ), After downloading, you can unzip it and use it , It's like using jdk First, find the folder where the file is located in the command line window , If you do not want to input a list of directories to query each time, you can also add the path of this file to the environment variable ( How to configure self search ).

When Web Proxy and Wget When you're ready, you can start running :

First, execute Web Proxy The program , And then through Wget Request to use a proxy and deliver Request

(Wget command :wget xxx.xxx.xx -e use_proxy=on -e http_proxy=127.0.0.1:8000), among “xxx.xxx.xx” It's the URL you want to ask for

3. Web Proxy Source code

import socket
def handleReq(clientSocket):
# recv data
# find the fileName
# judge if the file named "fileName" if existed
# if not exists, send req to get it
recvData = clientSocket.recv(1024).decode()
fileName = recvData.split()[1].split("//")[1].replace('/', '')
print("fileName: " + fileName)
try:
file = open(fileName, 'rb')
print("File is found in proxy server.")
responseMsg = file.readlines()
for i in range(0, len(responseMsg)):
clientSocket.sendall(responseMsg[i])
print("Send, done.")
except Exception:
try:
print("File is not exist.\nSend request to server...")
proxyClientSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
serverName = fileName.split(":")[0]
proxyClientSocket.connect((serverName, 80))
proxyClientSocket.sendall(recvData.encode())
responseMsg = proxyClientSocket.recv(4069)
print("File is found in server.")
proxyClientSocket.sendall(responseMsg)
print("Send, done.")
# cache
cache = open("./" + fileName, 'w')
cache.writelines(responseMsg.decode().replace('\r\n', '\n'))
cache.close()
print("Cache, done.")
except:
print("Connect timeout.")
def startProxy(port):
proxyServerSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
proxyServerSocket.bind(("", port))
proxyServerSocket.listen(0)
while True:
try:
print("Proxy is waiting for connecting...")
clientSocket, addr = proxyServerSocket.accept()
print("Connect established")
handleReq(clientSocket)
clientSocket.close()
except Exception as e:
print("error: {0}".format(e))
break
proxyServerSocket.close()
if __name__ == '__main__':
while True:
try:
port = int(input("choose a port number over 1024:"))
except ValueError:
print("Please input an integer rather than {0}".format(type(port)))
continue
else:
if port <= 1024:
print("Please input an integer greater than 1024")
continue
else:
break
startProxy(port)

4. Wget tool kit

Link to :https://pan.baidu.com/s/1Ae2_Cq9SYbKnfhhyJ1VhpQ
Extraction code :awsl 

&n

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