code: private void closeSelectors()
      {
          if (readSelector != null)
          {
              try
              {
                  readSelector.close();
              }
              catch (IOException e)
              {
                  LOGGER.debug("Error while closing read selector", e);
              }
          }
  
          if (writeSelector != null)
          {
              try
              {
                  writeSelector.close();
              }
              catch (IOException e)
              {
                  LOGGER.debug("Error while closing write selector", e);
              }
          }
      }
docs: Close the read and write selectors. This will prevent any further
  communication to the connected server through this manager until the
  selectors are {@link #openSelectors() opened} again. This should happen
  before {@link #redirectChannel() redirecting the channel}. If any errors
  occur here they will be logged, but not thrown.