Python Web Servers

serv_async.py

# python3
import asyncio
import sys

counter = 0

async def run_server(host, port):
  server = await asyncio.start_server(serve_client, host, port)
  await server.serve_forever()

async def serve_client(reader, writer):
  global counter
  cid = counter
  counter += 1
  print(f'Client #{cid} connected')

  request = await read_request(reader)
  if request is None:
    print(f'Client #{cid} unexpectedly disconnected')
  else:
    response = await handle_request(request)
    await write_response(writer, response, cid)

async def read_request(reader, delimiter=b'!'):
  request = bytearray()
  while True:
    chunk = await reader.read(4)
    if not chunk:
      # Клиент преждевременно отключился.
      break

    request += chunk
    if delimiter in request:
      return request

  return None

async def handle_request(request):
  await asyncio.sleep(5)
  return request[::-1]

async def write_response(writer, response, cid):
  writer.write(response)
  await writer.drain()
  writer.close()
  print(f'Client #{cid} has been served')

if __name__ == '__main__':
  asyncio.run(run_server('127.0.0.1', int(sys.argv[1])))

serv_proc.py

# python3
import os
import socket
import sys
import time

def run_server(port=53210):
  serv_sock = create_serv_sock(port)
  active_children = set()
  cid = 0
  while True:
    client_sock = accept_client_conn(serv_sock, cid)
    child_pid = serve_client(client_sock, cid)
    active_children.add(child_pid)
    reap_children(active_children)
    cid += 1

def serve_client(client_sock, cid):
  child_pid = os.fork()
  if child_pid:
    # Родительский процесс, не делаем ничего
    client_sock.close()
    return child_pid

  # Дочерний процесс:
  #  - читаем запрос
  #  - обрабатываем
  #  - записываем ответ
  #  - закрываем сокет
  #  - завершаем процесс (os._exit())
  request = read_request(client_sock)
  if request is None:
    print(f'Client #{cid} unexpectedly disconnected')
  else:
    response = handle_request(request)
    write_response(client_sock, response, cid)
  os._exit(0)

def reap_children(active_children):
  for child_pid in active_children.copy():
    child_pid, _ = os.waitpid(child_pid, os.WNOHANG)
    if child_pid:
      active_children.discard(child_pid)

def create_serv_sock(serv_port):
  serv_sock = socket.socket(socket.AF_INET,
                            socket.SOCK_STREAM,
                            proto=0)
  serv_sock.bind(('', serv_port))
  serv_sock.listen()
  return serv_sock

def accept_client_conn(serv_sock, cid):
  client_sock, client_addr = serv_sock.accept()
  print(f'Client #{cid} connected '
        f'{client_addr[0]}:{client_addr[1]}')
  return client_sock

def read_request(client_sock, delimiter=b'!'):
  request = bytearray()
  try:
    while True:
      chunk = client_sock.recv(4)
      if not chunk:
        # Клиент преждевременно отключился.
        return None

      request += chunk
      if delimiter in request:
        return request

  except ConnectionResetError:
    # Соединение было неожиданно разорвано.
    return None
  except:
    raise

def handle_request(request):
  time.sleep(5)
  return request[::-1]

def write_response(client_sock, response, cid):
  client_sock.sendall(response)
  client_sock.close()
  print(f'Client #{cid} has been served')


if __name__ == '__main__':
    run_server(port=int(sys.argv[1]))

serv_sync.py

# python3
import socket
import sys
import time

def run_server(port=53210):
  serv_sock = create_serv_sock(port)
  cid = 0
  while True:
    client_sock = accept_client_conn(serv_sock, cid)
    serve_client(client_sock, cid)
    cid += 1

def serve_client(client_sock, cid):
  request = read_request(client_sock)
  if request is None:
    print(f'Client #{cid} unexpectedly disconnected')
  else:
    response = handle_request(request)
    write_response(client_sock, response, cid)


def create_serv_sock(serv_port):
  serv_sock = socket.socket(socket.AF_INET,
                            socket.SOCK_STREAM,
                            proto=0)
  serv_sock.bind(('', serv_port))
  serv_sock.listen()
  return serv_sock

def accept_client_conn(serv_sock, cid):
    client_sock, client_addr = serv_sock.accept()
    print(f'Client #{cid} connected '
          f'{client_addr[0]}:{client_addr[1]}')
    return client_sock

def read_request(client_sock, delimiter=b'!'):
  request = bytearray()
  try:
    while True:
      chunk = client_sock.recv(4)
      if not chunk:
        # Клиент преждевременно отключился.
        return None

      request += chunk
      if delimiter in request:
        return request

  except ConnectionResetError:
    # Соединение было неожиданно разорвано.
    return None
  except:
    raise

def handle_request(request):
  time.sleep(5)
  return request[::-1]

def write_response(client_sock, response, cid):
  client_sock.sendall(response)
  client_sock.close()
  print(f'Client #{cid} has been served')


if __name__ == '__main__':
    run_server(port=int(sys.argv[1]))

serv_thread.py

# python3
import socket
import sys
import time
import threading

def run_server(port=53210):
  serv_sock = create_serv_sock(port)
  cid = 0
  while True:
    client_sock = accept_client_conn(serv_sock, cid)
    t = threading.Thread(target=serve_client,
                         args=(client_sock, cid))
    t.start()
    cid += 1

def serve_client(client_sock, cid):
  request = read_request(client_sock)
  if request is None:
    print(f'Client #{cid} unexpectedly disconnected')
  else:
    response = handle_request(request)
    write_response(client_sock, response, cid)

def create_serv_sock(serv_port):
  serv_sock = socket.socket(socket.AF_INET,
                            socket.SOCK_STREAM,
                            proto=0)
  serv_sock.bind(('', serv_port))
  serv_sock.listen()
  return serv_sock

def accept_client_conn(serv_sock, cid):
  client_sock, client_addr = serv_sock.accept()
  print(f'Client #{cid} connected '
        f'{client_addr[0]}:{client_addr[1]}')
  return client_sock

def read_request(client_sock, delimiter=b'!'):
  request = bytearray()
  try:
    while True:
      chunk = client_sock.recv(4)
      if not chunk:
        # Клиент преждевременно отключился.
        return None

      request += chunk
      if delimiter in request:
        return request

  except ConnectionResetError:
    # Соединение было неожиданно разорвано.
    return None
  except:
    raise

def handle_request(request):
  time.sleep(5)
  return request[::-1]

def write_response(client_sock, response, cid):
  client_sock.sendall(response)
  client_sock.close()
  print(f'Client #{cid} has been served')


if __name__ == '__main__':
    run_server(port=int(sys.argv[1]))

Hi.
asyncio.run added only in version 3.7: https://docs.python.org/3/library/asyncio-task.html#running-an-asyncio-program