Echo Server simultaneously with 1000 clients (lost messages + connecting to errors)

I am reading "Netty In Action V5". Reading to chapters 2.3 and 2.4, I tried with the EchoServer and EchoClient examples, when I tested one client connected to the server everything worked fine ... then I modified the example to allow multiple clients to connect to the server. My goal was to run a stresstest: 1000 clients will connect to the server, and each client will echo 100 messages to the server, and when all clients have finished, I get the total time of the whole process. The server was deployed on a Linux machine (VPS) and the clients were deployed on a window machine.

I got 2 problems when running stresstest:

Some clients received an error message:

java.io.IOException: An existing connection was forcibly closed by the remote host 
    at sun.nio.ch.SocketDispatcher.read0(Native Method)
    at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43)
    at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
    at sun.nio.ch.IOUtil.read(IOUtil.java:192)
    at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:379)
    at io.netty.buffer.UnpooledUnsafeDirectByteBuf.setBytes(UnpooledUnsafeDirectByteBuf.java:447)
    at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:881)
    at io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:242)
    at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:119)
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382)\at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354)
    at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:110)
    at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:137)
    at java.lang.Thread.run(Thread.java:745)

      

        
        
        
      

    

But some clients didn't receive the message from the server

Working environment:

• Netty-all-4.0.30.Final

• JDK1.8.0_25

• Echo clients have been deployed on Window 7 Ultimate

• Echo Server has been deployed on Linux Centos 6

NettyClient class:

public class NettyClient {
    private Bootstrap bootstrap;
    private EventLoopGroup group;

    public NettyClient(final ChannelInboundHandlerAdapter handler) {
        group = new NioEventLoopGroup();
        bootstrap = new Bootstrap();
        bootstrap.group(group);
        bootstrap.channel(NioSocketChannel.class);
        bootstrap.handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel channel) throws Exception {
                channel.pipeline().addLast(handler);
            }
        });
    }

    public void start(String host, int port) throws Exception {
        bootstrap.remoteAddress(new InetSocketAddress(host, port));
        bootstrap.connect();
    }

    public void stop() {
        try {
            group.shutdownGracefully().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

      

        
        
        
      

    

NettyServer class:

public class NettyServer {
    private EventLoopGroup parentGroup;
    private EventLoopGroup childGroup;
    private ServerBootstrap boopstrap;

    public NettyServer(final ChannelInboundHandlerAdapter handler) {
        parentGroup = new NioEventLoopGroup(300);
        childGroup = new NioEventLoopGroup(300);
        boopstrap = new ServerBootstrap();
        boopstrap.group(parentGroup, childGroup);
        boopstrap.channel(NioServerSocketChannel.class);
        boopstrap.childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel channel) throws Exception {
                channel.pipeline().addLast(handler);
            }
        });
    }

    public void start(int port) throws Exception {
        boopstrap.localAddress(new InetSocketAddress(port));
        ChannelFuture future = boopstrap.bind().sync();
        System.err.println("Start Netty server on port " + port);
        future.channel().closeFuture().sync();
    }

    public void stop() throws Exception {
        parentGroup.shutdownGracefully().sync();
        childGroup.shutdownGracefully().sync();
    }
}

      

        
        
        
      

    

EchoClient class

public class EchoClient {
    private static final String HOST = "203.12.37.22";
    private static final int PORT = 3344;
    private static final int NUMBER_CONNECTION = 1000;
    private static final int NUMBER_ECHO = 10;
    private static CountDownLatch counter = new CountDownLatch(NUMBER_CONNECTION);

    public static void main(String[] args) throws Exception {
        List<NettyClient> listClients = Collections.synchronizedList(new ArrayList<NettyClient>());
        for (int i = 0; i < NUMBER_CONNECTION; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        NettyClient client = new NettyClient(new EchoClientHandler(NUMBER_ECHO) {
                            @Override
                            protected void onFinishEcho() {
                                counter.countDown();
                                System.err.println((NUMBER_CONNECTION - counter.getCount()) + "/" + NUMBER_CONNECTION);
                            }
                        });
                        client.start(HOST, PORT);
                        listClients.add(client);
                    } catch (Exception ex) {
                        ex.printStackTrace();
                    }
                }
            }).start();
        }

        long t1 = System.currentTimeMillis();
        counter.await();
        long t2 = System.currentTimeMillis();
        System.err.println("Totla time: " + (t2 - t1));

        for (NettyClient client : listClients) {
            client.stop();
        }
    }

    private static class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {

        private static final String ECHO_MSG = "Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo Echo";
        private int numberEcho;
        private int curNumberEcho = 0;

        public EchoClientHandler(int numberEcho) {
            this.numberEcho = numberEcho;
        }

        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
            ctx.writeAndFlush(Unpooled.copiedBuffer(ECHO_MSG, CharsetUtil.UTF_8));
        }

        @Override
        protected void channelRead0(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
            curNumberEcho++;
            if (curNumberEcho >= numberEcho) {
                onFinishEcho();
            } else {
                ctx.writeAndFlush(Unpooled.copiedBuffer(ECHO_MSG, CharsetUtil.UTF_8));
            }
        }

        protected void onFinishEcho() {

        }

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

      

        
        
        
      

    

EchoServer class:

public class EchoServer {
    private static final int PORT = 3344;

    public static void main(String[] args) throws Exception {
        NettyServer server = new NettyServer(new EchoServerHandler());
        server.start(PORT);
        System.err.println("Start server on port " + PORT);
    }

    @Sharable
    private static class EchoServerHandler extends ChannelInboundHandlerAdapter {
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            ctx.write(msg);
        }

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

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