Netty学习

1.Netty是什么？

Netty是一个异步的、基于事件驱动的网络应用框架，可以用来快速开发可维护性的高性能协议的服务器和客户端。

Netty是一个NIO客户端服务端框架，它可以加速和简化网络应用程序的开发，比如协议服务和客户端。它极大的简化和流程化了网络编程，比如使用TCP和UDP的socket服务。
其结构图如下：

结构图.png

2.简单使用

• 服务端

 public void run() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_BACKLOG, 128)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new TimeServerHandler());
                        }
                    });

            // bind and start to accept incoming connections
            ChannelFuture f = b.bind(port).sync();
            // shut down your server
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

• 服务端handler

public class TimeServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        ctx.write(msg);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}

• 客户端

 public static void main(String[] args) throws Exception {
        String host = "127.0.0.1";
        int port = 8080;

        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            Bootstrap b = new Bootstrap();
            b.group(workerGroup);
            b.channel(NioSocketChannel.class);
            b.option(ChannelOption.SO_KEEPALIVE, true);
            b.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new TimeClientHandler());
                }
            });

            // Start the client
            ChannelFuture f = b.connect(host, port).sync();
            // Wait until the connection is closed
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
        }
    }

• 客户端Handler

public class TimeClientHandlerextends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        ctx.write(msg);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}