Netty版hello world

把书读薄(Netty in Action第二章)

通信流程图示

EchoClient代码

public class EchoClient {
    private final String host;
    private final int port;
    public EchoClient(String host,int port){
        this.host=host;
        this.port=port;
    }
    public void start() throws Exception{
        EventLoopGroup group = new NioEventLoopGroup();
        try{
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class)//指定NIO的传输方式
                    .remoteAddress(new InetSocketAddress(host,port))//指定远程地址
                    .handler(new ChannelInitializer<SocketChannel>() {//向channel的pipeline添加handler
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new EchoClientHandler());//channelHander交给pipeline
                        }
                    });
            ChannelFuture f = b.connect().sync();//连接到远程节点，阻塞直到连接完成
            f.channel().closeFuture().sync();//阻塞直到连接关闭
        }finally {
            group.shutdownGracefully().sync();//关闭线程池并且释放资源
        }
    }
    public static void main(String[]args) throws Exception{
        new EchoClient("localhost",8888).start();
    }
}

EchoClientHandler代码

public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.copiedBuffer("Hello world",CharsetUtil.UTF_8));
    }

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

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
        System.out.println("Client get:"+msg.toString(CharsetUtil.UTF_8));
    }
}

EchoServer代码

public class EchoServer {
    private final int port;

    public EchoServer(int port) {
        this.port = port;
    }
    public static void main(String[]args)throws Exception{
        new EchoServer(8888).start();
    }
    public void start() throws Exception{
        final EchoServerHandler handler = new EchoServerHandler();
        EventLoopGroup group = new NioEventLoopGroup();
        try{
            ServerBootstrap b = new ServerBootstrap();
            b.group(group).channel(NioServerSocketChannel.class).localAddress(new InetSocketAddress(port))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(handler);
                        }
                    });
            ChannelFuture f = b.bind().sync();
            f.channel().closeFuture().sync();
        }finally {
            group.shutdownGracefully().sync();
        }
    }
}

EchoServerHandler代码

public class EchoServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf in = (ByteBuf) msg;
        System.out.printf("Server get:"+in.toString(CharsetUtil.UTF_8));
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        //将目前暂存于ChannelOutboundBuffer中的消息在下一次flush或者writeAndFlush的时候冲刷到远程并关闭这个channel
        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
    }

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