back_end_proxyserver_159.py

import socket
import threading

BUFFER_SIZE = 4096
LOCAL_HOST = '127.0.0.1'
LOCAL_PORT = 9999

def handle_client(client_socket):
  request = client_socket.recv(BUFFER_SIZE)
  print(f'Received request: {request}')

  request_line = request.split(b'\n')[0]
  url = request_line.split(b' ')[1]

  http_pos = url.find(b'://')
  if http_pos == -1:
    temp = url
  else:
    temp = url[(http_pos + 3):]

  port_pos = temp.find(b':')

  server_pos = temp.find(b'/')
  if server_pos == -1:
    server_pos = len(temp)

  server = ""
  port = -1
  if port_pos == -1 or server_pos < port_pos:
    port = 80
    server = temp[:server_port]
  else:
    port = int((temp[(port_pos +1):])[:server_pos - port_pos - 1])
    server = temp[:port_pos]

  print(f'Connecting to {server.decode("utf-8")} on port {port}')

  try:
    proxy_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    proxy_socket.connect((server, port))
    proxy_socket.send(request)

    while True:
      data = proxy_socket.recv(BUFFER_SIZE)
      if not data:
        break
      client_socket.send(data)

    proxy_socket.close()
    client_socket.close()
  except Exception as e:
    print(f'Error: {e}')
    proxy_socket.close()
    client_socket.close()

def start_server():
  server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  server.bind((LOCAL_HOST, LOCAL_PORT))
  server.listen(5)
  print(f'[*] Listening on {LOCAL_HOST}:{LOCAL_PORT}')

  while True:
    client_socket, addr = server.accept()
    print(f'[*] Accepted connection from {addr[0]}:{addr[1]}')
    client_handler = threading.Thread(target=handle_cient, args=(client_socket,))
    client_handler.start()

if __name__ == '__main__':
  start_server()