Netty入门之客户端与服务端通信(二)

Netty入门之客户端与服务端通信(二)

一.简介

　　在上一篇博文中笔者写了关于Netty入门级的Hello World程序。书接上回，本博文是关于客户端与服务端的通信，感觉也没什么好说的了，直接上代码吧。

二.客户端与服务端的通信

2.1 服务端启动程序

public class MyServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try{
            ServerBootstrap serverBootstrap = new ServerBootstrap();

            serverBootstrap.group(bossGroup, workerGroup)
                           .channel(NioServerSocketChannel.class)
                           .childHandler(new MyInitializer());

            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally{
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

2.2 服务端通道初始化程序

public class MyInitializer extends ChannelInitializer<SocketChannel>{

    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline =  ch.pipeline();
        /**
         * LengthFieldBasedFrameDecoder: 基于长度属性的帧解码器。
         * 客户端传递过来的数据格式为：
         *  BEFORE DECODE (14 bytes)         AFTER DECODE (14 bytes)
         *    +--------+----------------+      +--------+----------------+
         *    | Length | Actual Content |----->| Length | Actual Content |
         *    | 0x000C | "HELLO, WORLD" |      | 0x000C | "HELLO, WORLD" |
         *    +--------+----------------+      +--------+----------------+
         * 5个参数依次为：1.(maxFrameLength)每帧数据的最大长度.
         *              2.(lengthFieldOffset)length属性在帧中的偏移量。
         *           3.(lengthFieldLength)length属性的长度，需要与客户端 LengthFieldPrepender设置的长度一致，
         *               值的取值只能为1, 2, 3, 4, 8
         *           4.(lengthAdjustment)长度调节值, 当信息长度包含长度时候，用于修正信息的长度。
         *           5.(initialBytesToStrip)在获取真实的内容的时候，需要忽略的长度(通常就是length的长度)。
         *
         * 参考： http://blog.csdn.net/educast/article/details/47706599
         */
        pipeline.addLast("lengthFieldBasedFrameDecoder",
                            new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 2, 0, 2));
        /**
         * LengthFieldPrepender: length属性在帧中的长度。只能为1,2,3,4,8。
         * 该值与对应的客户端(或者服务端)在解码时候使用LengthFieldBasedFrameDecoder中所指定的lengthFieldLength
         * 的值要保持一致。
         */
        pipeline.addLast("lengthFieldPrepender", new LengthFieldPrepender(3));
        //StringDecoder字符串的解码器, 主要用于处理编码格式
        pipeline.addLast("stringDecoder", new StringDecoder(CharsetUtil.UTF_8));
        //StringDecoder字符串的编码器，主要用于指定字符串的编码格式
        pipeline.addLast("stringEncoder", new StringEncoder(CharsetUtil.UTF_8));

        pipeline.addLast(new MyHandler()); //自定义的Handler
    }
}

2.3 自定义Handler

public class MyHandler extends SimpleChannelInboundHandler<String>{

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + ":" + msg);
        ctx.channel().writeAndFlush("from server: 草泥马");
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        System.out.println(System.currentTimeMillis() + "********");
        System.out.println("server handler added**********");
    }

    @Override
    public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println(System.currentTimeMillis() + "********");
        System.out.println("server channel register****");
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(System.currentTimeMillis() + "********");
        System.out.println("server channel actieve****");
    }

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

2.4客户端启动程序

public class MyClient {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();

        try{
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class).handler(new ClientInitializer());

            ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally{
            eventLoopGroup.shutdownGracefully();
        }
    }
}

2.5客户端通道初始化

public class ClientInitializer extends ChannelInitializer<SocketChannel>{

    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline =  ch.pipeline();
        pipeline.addLast("lengthFieldBasedFrameDecoder",
                            new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 2, 0, 2));
        pipeline.addLast("lengthFieldPrepender", new LengthFieldPrepender(3));
        pipeline.addLast("stringDecoder", new StringDecoder(CharsetUtil.UTF_8));
        pipeline.addLast("stringEncoder", new StringEncoder(CharsetUtil.UTF_8));

        pipeline.addLast(new MyClientHandler());
    }
}

2.5客户端自定义Handler

public class MyClientHandler extends SimpleChannelInboundHandler<String>{

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress());
        System.out.println(msg);
        ctx.channel().writeAndFlush("to Server: 草泥马");
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(System.currentTimeMillis() + "...........");
        ctx.channel().writeAndFlush("来自于客户端的问候！");
        System.out.println("client channel Active...");
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        System.out.println(System.currentTimeMillis() + "...........");
        System.out.println("client hanlder added...");
    }

    @Override
    public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println(System.currentTimeMillis() + "...........");
        System.out.println("client channel register...");
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("client channel inactive...");
    }

    @Override
    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println("client channel unregister...");
    }

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

三. 运行测试

运行服务端启动代码，然后在运行客户端启动代码，就可以看见千万只"草泥马"在崩腾。