Message is not received by client in Netty when there are more number of messages sent to Server

Question

I implemented a very basic EchoClient and EchoServer using the Netty package in JAVA. I am very much new to Netty . Below are the codes for my client , clientHandler , server and serverHandler.

My Client

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", 11235).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
                        public void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new EchoClientHandler());
                        }
                    });
            ChannelFuture future = b.connect().sync();
            future.channel().closeFuture().sync();

        } finally {
            group.shutdownGracefully().sync();
        }

    }
}

My ClientHandler

public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf>{

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        System.out.println("Connected");
        int i = 0;
        while (i < 1000) {
            ctx.writeAndFlush(Unpooled.copiedBuffer("Netty MAY rock!\n", CharsetUtil.UTF_8));
            i++;
        }
    }

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

    }

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

My Server

public class EchoServer {

    private final int port;

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

    public static void main(String[] args) throws Exception {
        new EchoServer(11235).start();
    }

    public void start() throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(group)
                    .channel(NioServerSocketChannel.class)
                    .localAddress(new InetSocketAddress(port))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            System.out.println("New client connected: " + ch.localAddress());
                            ch.pipeline().addLast(new EchoServerHandler());
                        }
                    });
            ChannelFuture f = b.bind().sync();
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully().sync();
        }
    }
}

My SeverHandler

public class EchoServerHandler extends ChannelInboundHandlerAdapter {

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

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

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

Now the problem is : when I write the while loop in the ClientHandler as i<10 or i<100 both the Server and Client can receive the sent messages but if I increase the iterations upto 1000 and 10000, the Sever is receiving message but not the client. Even the server is unable to receive 10000 messages(only some of the messages are received).

Answer 1

You close your server channel immediately after the first reading. Please remove .addListener(ChannelFutureListener.CLOSE) in channelReadComplete of your EchoServerHandler class.