[netty] On the netty server side, the main sending command is sent. If the other party's client does not receive it, how to set it to resend? ?

public class MessageHandler extends ChannelInboundHandlerAdapter implements ChannelOutboundHandler {

    @Override

    public void channelActive(ChannelHandlerContext ctx) throws Exception {

        Map newMap = new HashMap<>();

        // Resend the message every three seconds

        ctx.executor().scheduleAtFixedRate(() -> {

            if (map.size() > 0) 

            {

                map.forEach((k, v) -> {

                    ctx.writeAndFlush(v.data);

                    v.times = v.times + 1;

                    if (v.times < 3) 

                    {

                        // Keep unsent three times.

                        newMap.put(v.id, v);

                    }

                });

            }

            map = newMap;

        }, 3, 3, TimeUnit.SECONDS);

    }

}