netty实现UDP多播

广播方

/**
 * 类说明：广播
 */
public class LogEventBroadcaster {
    private final EventLoopGroup group;
    private final Bootstrap bootstrap;

    public LogEventBroadcaster(InetSocketAddress remoteAddress) {
        group = new NioEventLoopGroup();
        bootstrap = new Bootstrap();
        //引导该 NioDatagramChannel（无连接的）
        bootstrap.group(group).channel(NioDatagramChannel.class)

             //设置 SO_BROADCAST 套接字选项
             .option(ChannelOption.SO_BROADCAST,true)

             .handler(new LogEventEncoder(remoteAddress));
    }

    public void run() throws Exception {
        //绑定 Channel
        Channel ch = bootstrap.bind(0).sync().channel();
        long count = 0;

        //启动主处理循环，模拟日志发送
        for (;;) {
            ch.writeAndFlush(new LogMsg(null, ++count,
                    LogConst.getLogInfo()));
            try {
                //休眠 2 秒，如果被中断，则退出循环；
                Thread.sleep(2000);

            } catch (InterruptedException e) {
                Thread.interrupted();
                break;
            }
        }
    }

    public void stop() {
        group.shutdownGracefully();
    }

    public static void main(String[] args) throws Exception {

        //创建并启动一个新的 UdpQuestionSide 的实例
        LogEventBroadcaster broadcaster = new LogEventBroadcaster(
                //表明本应用发送的报文并没有一个确定的目的地，也就是进行广播
                new InetSocketAddress("255.255.255.255",
                        LogConst.MONITOR_SIDE_PORT));
        try {
            broadcaster.run();
        }
        finally {
            broadcaster.stop();
        }
    }
}

编码器

/**
 * 类说明：编码，将实际的日志实体类编码为DatagramPacket
 */
public class LogEventEncoder extends MessageToMessageEncoder {
    private final InetSocketAddress remoteAddress;

    //LogEventEncoder 创建了即将被发送到指定的 InetSocketAddress
    // 的 DatagramPacket 消息
    public LogEventEncoder(InetSocketAddress remoteAddress) {
        this.remoteAddress = remoteAddress;
    }

    @Override
    protected void encode(ChannelHandlerContext channelHandlerContext,
                          LogMsg logMsg, List