第四章Netty第四节案例实现echo server

需求

实现一个echo server。通俗的说就是客户端发送什么就会接受到什么。echo的意思“回声”。

服务端

 new ServerBootstrap()
                .group(new NioEventLoopGroup())
                .channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer<NioSocketChannel>() {
                    @Override
                    protected void initChannel(NioSocketChannel ch) {
                        ch.pipeline().addLast(new ChannelInboundHandlerAdapter(){
                            @Override
                            public void channelRead(ChannelHandlerContext ctx, Object msg) {
                                ByteBuf buffer = (ByteBuf) msg;
                                System.out.println(buffer.toString(Charset.defaultCharset()));

                                // 建议使用 ctx.alloc() 创建 ByteBuf
                                ByteBuf response = ctx.alloc().buffer();
                                response.writeBytes(buffer);
                                ctx.writeAndFlush(response);

                                // 思考：需要释放 buffer 吗
                                buffer.release();// 没有向后传递了，所以应该释放？
                                // 思考：需要释放 response 吗
                                response.release();// 没有向后传递了，所以应该释放？
                            }
                        });
                    }
                }).bind(8090);

客户端

 NioEventLoopGroup group = new NioEventLoopGroup();
        Channel channel = new Bootstrap()
                .group(group)
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<NioSocketChannel>() {
                    @Override
                    protected void initChannel(NioSocketChannel ch) throws Exception {
                        ch.pipeline().addLast(new StringEncoder());
                        ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                            @Override
                            public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                                ByteBuf buffer = (ByteBuf) msg;
                                System.out.println(buffer.toString(Charset.defaultCharset()));

                                // 思考：需要释放 buffer 吗
                                buffer.release();//可以释放。不释放，tail会释放。能自己释放还是自己释放。
                            }
                        });
                    }
                }).connect("127.0.0.1", 8090).sync().channel();
        channel.closeFuture().addListener(future -> {
            group.shutdownGracefully();
        });
        new Thread(() -> {
            Scanner scanner = new Scanner(System.in);
            while (true) {
                String line = scanner.nextLine();
                if ("q".equals(line)) {
                    channel.close();
                    break;
                }
                channel.writeAndFlush(line);
            }
        }).start();

运行结果

客户端打印输出

hello
hello
hey
hey