new_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  """Concurrent server using gevent
  """
  
  import server
  from gevent import socket as g
  
  
  def return_concurrent_request():
      ADDR = ('127.0.0.1', 8000)
      socket = g.socket(
          g.AF_INET, g.SOCK_STREAM, g.IPPROTO_IP
      )
  
      socket.bind(ADDR)
      socket.listen(5)
      while True:
          try:
              conn, addr = socket.accept()
              request = ""
              while True:
                  msg = conn.recv(1024)
                  request = request + msg
                  if len(msg) < 1024:
                      break
              try:
                  response = server.response_ok(server.parse_request(request))
              except ValueError as detail:
                  response = server.response_error(b"400", str(detail))
              except LookupError as detail:
                  response = server.response_error(b"404", str(detail))
              except AttributeError as detail:
                  response = server.response_error(b"405", str(detail))
              except NotImplementedError as detail:
                  response = server.response_error(b"500", str(detail))
              except UserWarning as detail:
                  response = server.response_error(b"403", str(detail))
              conn.sendall(response)
              conn.close()
          except KeyboardInterrupt:
              break
  
  
  if __name__ == "__main__":
      return_concurrent_request()
  
subject: Add 'concurrent.py'