netty之udp单播demo

提问端

/**
 * @author yun
 * 类说明：发送端
 */
public class UdpQuestionSide {

    public final static String QUESTION = "告诉我一句古诗";

    public void run(int port) throws Exception{

        EventLoopGroup group  = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
                    /*由于我们用的是UDP协议，所以要用NioDatagramChannel来创建*/
                    .channel(NioDatagramChannel.class)
                    .handler(new QuestoinHandler());
            //不需要建立连接
            Channel ch = b.bind(0).sync().channel();
            //将UDP请求的报文以DatagramPacket打包发送给接受端
            ch.writeAndFlush(new DatagramPacket(
                    Unpooled.copiedBuffer(QUESTION,CharsetUtil.UTF_8),
                    new InetSocketAddress("127.0.0.1",port)
            ));
            //不知道接收端能否收到报文，也不知道能否收到接收端的应答报文
            // 所以等待15秒后，不再等待，关闭通信
            if(!ch.closeFuture().await(15000)){
                System.out.println("查询超时！");
            }
        } catch (Exception e) {
            group.shutdownGracefully();
        }
    }
    public static void main(String [] args) throws Exception{
        int answerPort = 8080;

        new UdpQuestionSide().run(answerPort);
    }
}

提问端handler

/**
 * @author yun
 * 类说明：提问端的Handler，读取服务器的应答
 */
public class QuestoinHandler extends
        SimpleChannelInboundHandler<DatagramPacket> {

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg)
            throws Exception {
        //获得应答，DatagramPacket提供了content()方法取得报文的实际内容
        String response = msg.content().toString(CharsetUtil.UTF_8);
        if (response.startsWith(UdpAnswerSide.ANSWER)) {
            System.out.println(response);
            ctx.close();
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

应答端

/**
 * @author yun
 * 类说明：应答端
 */
public class UdpAnswerSide {

    public final static String ANSWER = "古诗来了：";

    public void run(int port) throws Exception{
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            /*和tcp的不同，udp没有接受连接的说法，所以即使是接收端，也使用Bootstrap*/
            Bootstrap b = new Bootstrap();
            /*由于我们用的是UDP协议，所以要用NioDatagramChannel来创建*/
            b.group(group)
                .channel(NioDatagramChannel.class)
                .handler(new AnswerHandler());
            //没有接受客户端连接的过程，监听本地端口即可
            ChannelFuture f = b.bind(port).sync();
            System.out.println("应答服务已启动.....");
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }
    public static void main(String [] args) throws Exception{
        int port = 8080;
        new UdpAnswerSide().run(port);
    }
}

应答端handler

/**
 * @author yun
 * 类说明：应答Handler
 */
public class AnswerHandler extends
        SimpleChannelInboundHandler<DatagramPacket> {

    /*应答的具体内容从常量字符串数组中取得，由nextQuote方法随机获取*/
    private static final String[] DICTIONARY = {
            "只要功夫深，铁棒磨成针。",
            "旧时王谢堂前燕,飞入寻常百姓家。",
            "洛阳亲友如相问，一片冰心在玉壶。",
            "一寸光阴一寸金，寸金难买寸光阴。",
            "老骥伏枥，志在千里，烈士暮年，壮心不已" };
    private static Random r = new Random();
    private String nextQuote(){
        return DICTIONARY[r.nextInt(DICTIONARY.length-1)];
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx,
                                DatagramPacket packet)
            throws Exception {

        //获得请求
        String req = packet.content().toString(CharsetUtil.UTF_8);
        System.out.println(req);
        if(UdpQuestionSide.QUESTION.equals(req)){
            /**
             * 重新 new一个DatagramPacket对象，我们通过packet.sender()
             * 来获取发送者的地址。
             * 重新发送出去！
             */
            ctx.writeAndFlush(
                    new DatagramPacket(
                            Unpooled.copiedBuffer(
                                    UdpAnswerSide.ANSWER+nextQuote(),
                                    CharsetUtil.UTF_8),
                            packet.sender()));
        }
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception {
        ctx.close();
        cause.printStackTrace();
    }
}