code: def start_server(app: web.Application = None, port: int = None,
                   address: str = None, **kwargs: Any) -> HTTPServer:
      
      app = app or get_app()
      port = port if port is not None else config.port
      address = address if address is not None else config.address
  
      server = app.listen(port, address=address)
      app.server = server
      app.loop = asyncio.get_event_loop()
      server_config['address'] = address
      for sock in server._sockets.values():
          if sock.family == socket.AF_INET:
              server_config['port'] = sock.getsockname()[1]
              break
      return server
docs: Start server with ``app`` on ``localhost:port``.
  
      If port is not specified, use command line option of ``--port``.