Netty入門之客戶端與服務端通信(二)

一.簡介

　　在上一篇博文中筆者寫了關於Netty入門級的Hello World程序。書接上回，本博文是關於客戶端與服務端的通信，感覺也沒什麽好說的了，直接上代碼吧。

二.客戶端與服務端的通信

2.1 服務端啟動程序

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 服務端通道初始化程序

public class MyInitializer extends ChannelInitializer<SocketChannel>{

    @Override
    
 
protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline =  ch.pipeline();
        /**
         * LengthFieldBasedFrameDecoder: 基於長度屬性的幀解碼器。
         * 客戶端傳遞過來的數據格式為：
         *  BEFORE DECODE (14 bytes)         AFTER DECODE (14 bytes)  
         *    +--------+----------------+      +--------+----------------+  
         *    | Length | Actual Content |----->| Length | Actual Content |  
         *    | 0x000C | "HELLO, WORLD" |      | 0x000C | "HELLO, WORLD" |  
         *    +--------+----------------+      +--------+----------------+  
         * 5個參數依次為：1.(maxFrameLength)每幀數據的最大長度.
         *              2.(lengthFieldOffset)length屬性在幀中的偏移量。
         *           3.(lengthFieldLength)length屬性的長度，需要與客戶端 LengthFieldPrepender設置的長度一致，
         *               值的取值只能為1, 2, 3, 4, 8
         *           4.(lengthAdjustment)長度調節值, 當信息長度包含長度時候，用於修正信息的長度。
         *           5.(initialBytesToStrip)在獲取真實的內容的時候，需要忽略的長度(通常就是length的長度)。
         *           
         * 參考： http://blog.csdn.net/educast/article/details/47706599
         */
        pipeline.addLast("lengthFieldBasedFrameDecoder", 
                            new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 2, 0, 2));
        /**
         * LengthFieldPrepender: length屬性在幀中的長度。只能為1,2,3,4,8。
         * 該值與對應的客戶端(或者服務端)在解碼時候使用LengthFieldBasedFrameDecoder中所指定的lengthFieldLength
         * 的值要保持一致。
         */
        pipeline.addLast("lengthFieldPrepender", new LengthFieldPrepender(3));
        //StringDecoder字符串的解碼器, 主要用於處理編碼格式
        pipeline.addLast("stringDecoder", new StringDecoder(CharsetUtil.UTF_8));
        //StringDecoder字符串的編碼器，主要用於指定字符串的編碼格式
        pipeline.addLast("stringEncoder", new StringEncoder(CharsetUtil.UTF_8));
        
        pipeline.addLast(new MyHandler()); //自定義的Handler
    }
}

2.3 自定義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: 草泥馬");
    }
    
    @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客戶端啟動程序

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客戶端通道初始化

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客戶端自定義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: 草泥馬");
    }
    
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(System.currentTimeMillis() + "...........");
        ctx.channel().writeAndFlush("來自於客戶端的問候！");
        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. 運行測試

運行服務端啟動代碼，然後在運行客戶端啟動代碼，就可以看見千萬只"草泥馬"在崩騰。

Netty入門之客戶端與服務端通信(二)