code: protected Connector createBaseListener(Configuration conf)
        throws IOException {
      Connector ret;
      if (conf.getBoolean("hadoop.http.bio", false)) {
        SocketConnector conn = new SocketConnector();
        conn.setAcceptQueueSize(4096);
        conn.setResolveNames(false);
        ret = conn;
      } else {
        SelectChannelConnector conn = new SelectChannelConnector();
        conn.setAcceptQueueSize(128);
        conn.setResolveNames(false);
        conn.setUseDirectBuffers(false);
        ret = conn;
      }
      ret.setLowResourceMaxIdleTime(10000);
      ret.setHeaderBufferSize(conf.getInt("hadoop.http.header.buffer.size", 4096));
      ret.setMaxIdleTime(conf.getInt("dfs.http.timeout", 200000));
      return ret;
    }
docs: Create a required listener for the Jetty instance listening on the port
  provided. This wrapper and all subclasses must create at least one
  listener.