code: public EpollSocketChannelConfig setTcpKeepIdle(int seconds) {
          try {
              ((EpollSocketChannel) channel).socket.setTcpKeepIdle(seconds);
              return this;
          } catch (IOException e) {
              throw new ChannelException(e);
          }
      }
docs: Set the {@code TCP_KEEPIDLE} option on the socket. See {@code man 7 tcp} for more details.