服务端向设备写信息：

        Instant currentTs = Instant.ofEpochMilli(System.currentTimeMillis());
        String currentTsSTr = currentTs.atZone(ZoneId.systemDefault()).format(formatter);
        String tid = "00000000251200000014";
        Channel heartChannel = IJT808Cache.SESSIONS.getIfPresent(tid);
        if(heartChannel != null) {
            String connStatus = heartChannel.isActive() ? "激活" : "失效";
            heartChannel.writeAndFlush(Utils.hexToBytes("7E7E")).addListener(future -> {
                if(future.isSuccess()) {
                    logger.info(String.format("%s %s %s, 发送消息成功",currentTsSTr ,tid, connStatus));
                } else {
                    logger.info(String.format("%s %s %s, 发送消息失败",currentTsSTr ,tid, connStatus));
                    heartChannel.close();
                }
            });
        } else {
            logger.info(String.format("%s %s 连接不存在",currentTsSTr ,tid));
        }

定时下发消息，会让 IdleStateHandler 处理器失效

pipeline.addLast(new IdleStateHandler(180, 0, 0, TimeUnit.SECONDS));

Netty 读取数据后，要恢复标记位：

byte[] byteArray1 = new byte[decodeData.readableBytes()];
decodeData.readBytes(byteArray1);
decodeData.resetReaderIndex(); // 恢复到标记位
String newMsgText1 = Utils.bytesToHex(byteArray1);