Netty入门Demo

1. 添加依赖

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.34.Final</version>
</dependency>

2. 编写消息接收处理器

public class NettyServerHandler extends ChannelInboundHandlerAdapter{

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            ByteBuf in = (ByteBuf)msg;
            System.out.println(ctx.name()+"发送:"+in.toString(io.netty.util.CharsetUtil.US_ASCII));
        } finally {
            //释放传递给处理程序的引用计数对象
            ReferenceCountUtil.release(msg);
        }
    }

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

3. 编写服务器

public class NettyServerDemo {
    private int port;

    public NettyServerDemo(int port) {
        this.port = port;
    }

    public void run() throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new NettyServerHandler());
                        }
                    })
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);

            //绑定端口，并等待连接
            ChannelFuture f = b.bind(port).sync();

            // 关闭服务
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port;
        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
        } else {
            port = 8080;
        }
        new NettyServerDemo(port).run();
    }
}

4. 测试

1. 启动NettyServerDemo
2. 命令行中输入: telnet localhost 8080
   如果找不到Telnet命令，说明Telnet客户端没有打开，在控制面板中—> 程序 ——> 打开或关闭Windows功能
   
   当输入信息后，服务器端会收到点击的键，并输出出来