1. Netty 核心组件

EventLoop(Group)
Channel
事件
ChannelHandler
ChannelPipeline
ChannelFuture

2. 流程

3. 使用示例

public class EchoServer {
    private final int port;

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

    public void start() throws InterruptedException {
        final EchoServerHandler serverHandler = new EchoServerHandler();
        /*线程组*/
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            /*服务端启动必备*/
            ServerBootstrap b = new ServerBootstrap();
            b.group(group)
                    .channel(NioServerSocketChannel.class)/*指定使用NIO的通信模式*/
                    .localAddress(new InetSocketAddress(port))/*指定监听端口*/
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) {
                            ch.pipeline().addLast(serverHandler);
                        }
                    });
            ChannelFuture f = b.bind().sync();/*异步绑定到服务器，sync()会阻塞到完成*/
            f.channel().closeFuture().sync();/*阻塞当前线程，直到服务器的ServerChannel被关闭*/
        } finally {
            group.shutdownGracefully().sync();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        EchoServer echoServer = new EchoServer(9999);
        echoServer.start();
    }
}

@ChannelHandler.Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        ByteBuf in = (ByteBuf) msg;
        System.out.println("Hello Client");
        ctx.writeAndFlush(in);
        //ctx.close();
    }

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

public class EchoClient {

    private final int port;
    private final String host;

    public EchoClient(int port, String host) {
        this.port = port;
        this.host = host;
    }

    public void start() throws InterruptedException {
        /*线程组*/
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            /*客户端启动必备*/
            Bootstrap b = new Bootstrap();
            b.group(group)
                    .channel(NioSocketChannel.class)/*指定使用NIO的通信模式*/
                    .remoteAddress(new InetSocketAddress(host, port))/*指定服务器的IP地址和端口*/
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) {
                            ch.pipeline().addLast(new EchoClientHandler());
                        }
                    });
            ChannelFuture f = b.connect().sync();/*异步连接到服务器，sync()会阻塞到完成*/
            f.channel().closeFuture().sync();/*阻塞当前线程，直到客户端的Channel被关闭*/
        } finally {
            group.shutdownGracefully().sync();

        }
    }

    public static void main(String[] args) throws InterruptedException {
        new EchoClient(9999, "127.0.0.1").start();
    }
}

public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
    /*读取到网络数据后进行业务处理*/
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
        System.out.println("client Accept：" + msg.toString(CharsetUtil.UTF_8));
        ctx.close();
    }

    /*channel活跃后，做业务处理*/
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.copiedBuffer("Hello,Netty", CharsetUtil.UTF_8));
    }
}