code: def close(self):
          
          if self.closed is False:
              self._client.close()
              self.closed = True
              if self.debug is True:
                  print('close')
          if self.debug is True:
              print("closed")
docs: 关闭与远端的连接.
  
          判断标志位closed是否为False,如果是则关闭,否则不进行操作