02_Netty实现的Echo服务器和客户端

【Echo服务端】

【EchoServer】

public class EchoServer {
    private final int port;

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

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

    public void start() throws Exception {
        NioEventLoopGroup group = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();   //创建ServerBootstrap
            b.group(group)
                    .channel(NioServerSocketChannel.class)   //指定NIO的传输Channel
                    .localAddress(new InetSocketAddress(port))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel channel) throws Exception {
                            channel.pipeline().addLast(new EchoServerHandler());  //添加EchoServerHandler到Channel的ChannelPipeline
                        }
                    });
            ChannelFuture future = b.bind().sync();  //绑定服务器，sync等待服务器关闭
            System.out.println(EchoServer.class.getName() + " started and listen on " + future.channel().localAddress());
            future.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully().sync();
        }
    }

}

【EchoServerHandler】

public class EchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf  in = (ByteBuf)msg;
        System.out.println("Server received:"+in.toString(CharsetUtil.UTF_8));
        ctx.write(in);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER)
                .addListener(ChannelFutureListener.CLOSE);
    }

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

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("Server is Active......");
    }


}

[ 说明 ] 

Echo的Handler实现了服务器的业务，决定了连接创建以后和收到信息后该如何处理。

ChannelInboundHandler的实现方法作用
channelRead()         //每次收到信息都会回调
channelReadComplete() //channelRead执行结束时回调
exceptionCaught()     //执行异常情况下会被回调。

【Echo客户端】

【EchoClient】

public class EchoClient {

    private final String host;
    private final int port;

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

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

    public void start() throws Exception{
        EventLoopGroup group = new NioEventLoopGroup();
        try{
            Bootstrap b = new Bootstrap();
            b.group(group)
                    .channel(NioSocketChannel.class)
                    .remoteAddress(new InetSocketAddress(host,port))
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel channel) throws Exception {
                            channel.pipeline().addLast(
                                    new EchoClientHandler()
                            );
                        }
                    });
            ChannelFuture future = b.connect().sync();
            future.channel().closeFuture().sync();
        }finally {
            group.shutdownGracefully();
        }
    }
}

【EchoClientHandler】

public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("client is active......");
        ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!", CharsetUtil.UTF_8));
    }

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, ByteBuf in) throws Exception {
        System.out.println("client received:"+ in.toString(CharsetUtil.UTF_8));
    }

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

}

【运行结果】

[ 服务端 ]

[ 客户端 ]