使用其它客户端软件为何接收不了netty服务端返回的数据呢

Question

我编了一个java程序，功能是实现netty的服务端，开启9400端口接收数据。

public class echoServer {
    private int port;
    public echoServer(int port) { this.port = port; }
    public void start() {
        EventLoopGroup boosGroup = new NioEventLoopGroup(1); //bossGroup
        EventLoopGroup workerGroup = new NioEventLoopGroup(); //workGroup
        try{ServerBootstrap sbs = new ServerBootstrap().group(boosGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .localAddress(new InetSocketAddress(port))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        protected void initChannel(SocketChannel ch) {
                            ch.pipeline().addLast("decoder", new StringDecoder());
                            ch.pipeline().addLast("encoder", new StringEncoder());
                            ch.pipeline().addLast(new echoServerHandler());
                        }
                    }).option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);
            ChannelFuture future = sbs.bind(port).sync();
            System.out.println("Server start listen at " + port);
            future.channel().closeFuture().sync();
        } catch (Exception e) {
            boosGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
    public static void main(String[] args) {
        new echoServer(9400).start();
    }
}

客户端使用的软件为Insomnia，向9400端口发送一个消息。

想尝试将服务端接收到的消息原样返回给Insomnia。

public class echoServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("Server channelRead....");
        System.out.println(ctx.channel().remoteAddress()+"->Server :"+msg.toString());
        ctx.write("Server write"+msg); //原样返回
        ctx.flush();
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

但却失败了

想问一问具体原因是什么？

以及请问如何解决？

Answer 1

必须是ByteBuf或FileRegion类型

ctx.writeAndFlush(Unpooled.copiedBuffer("hello world", CharsetUtil.UTF_8));