text: from gevent import wsgi
  
  def hello_world(environ, start_response):
      status = '200 OK'
      res = "Hello world!"
      response_headers = [('Content-type','text/plain')]
      start_response(status, response_headers)
      return [res]
  
  wsgi.WSGIServer(('', 8001), hello_world, log=None).serve_forever()
  