How to handle udp byte array with netty？

Question

I used netty to accept the byte array transmitted by UDP protocol.However, once the array exceeds 8 bits, an error will occur.example,when I send byte array [c 1 2 0 0 0 5 12 34 ff 0 59],netty will receive [12, 1, 2, 0, 0, 0, 5, 18, 3, 3, 15, 0 89]. Server`s code:

@Component
public class TestUdp implements ApplicationRunner {
    private void start(){
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        try {
            bootstrap.group(bossGroup)
                    .channel(NioDatagramChannel.class)
                    .option(ChannelOption.SO_BROADCAST,true)
                    .option(ChannelOption.RCVBUF_ALLOCATOR, new FixedRecvByteBufAllocator(65535))
                    .handler(new ChannelInitializer<NioDatagramChannel>() {
                        @Override
                        protected void initChannel(NioDatagramChannel nioDatagramChannel) throws Exception {
                            nioDatagramChannel.pipeline().addLast(new MyUdpDecoder());
                        }
                    });

            ChannelFuture future = bootstrap.bind(9510).sync();
            future.channel().closeFuture().await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            bossGroup.shutdownGracefully();
        }
    }
    @Override
    public void run(ApplicationArguments args) throws Exception {
        start();
    }

decoder`s code:

@Slf4j
public class MyUdpDecoder extends MessageToMessageDecoder<DatagramPacket> {
    @Override
    protected void decode(ChannelHandlerContext ctx, DatagramPacket packet, List<Object> list) throws Exception {
        ByteBuf buf = packet.content();
        byte[] bytes = new byte[buf.readableBytes()];
        buf.readBytes(bytes);
        int[] reqInt = getResult(bytes);
        log.info("data："+ Arrays.toString(reqInt));
    }
    public static int[] getResult(byte[] obj){
        int first = 0xff & obj[0];
        obj = Arrays.copyOf(obj, first);
        int[] result = new int[obj.length];
        result[0] = first;
        for (int i = 1; i < obj.length; i++) {
            result[i] = 0xff & obj[i];
        }
        return result;
    }
}

you can copy the code and run in any springboot project.Thank you very much for your help!