StO: Create one to many TCP-proxy

MultiplierClientHandler.java

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class MultiplierClientHandler extends ChannelInboundHandlerAdapter {

    private final ByteBuf message;

    public MultiplierClientHandler(ByteBuf buf) {
        message = buf;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ctx.writeAndFlush(message);
        ctx.close();
    }

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

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

MultiplierServer.java

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

public final class MultiplierServer {

    static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));

    public static void main(String[] args) throws Exception {
        // Configure the server.
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
             .channel(NioServerSocketChannel.class)
             .option(ChannelOption.SO_BACKLOG, 100)
             .handler(new LoggingHandler(LogLevel.INFO))
             .childHandler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 public void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast(new LoggingHandler(LogLevel.INFO));
                     p.addLast(new MultiplierServerHandler());
                 }
             });
            // Start the server.
            ChannelFuture f = b.bind(PORT).sync();
            // Wait until the server socket is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down all event loops to terminate all threads.
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

MultiplierServerHandler.java

import com.karlsoft.wrapper.config.HostInfo;
import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import java.util.LinkedList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

public class MultiplierServerHandler extends ChannelInboundHandlerAdapter {

    private static final Logger LOG = Logger.getLogger(MultiplierServerHandler.class.getName());
    private final List<HostInfo> HOSTS = new LinkedList<>();
    private ByteBuf buf;

    public MultiplierServerHandler() {
        HOSTS.add(new HostInfo("127.0.0.1", 10000));
        HOSTS.add(new HostInfo("127.0.0.1", 20000));
        HOSTS.add(new HostInfo("127.0.0.1", 30000));
        HOSTS.add(new HostInfo("127.0.0.1", 40000));
        HOSTS.add(new HostInfo("127.0.0.1", 50000));
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        buf = (ByteBuf) msg;
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws InterruptedException {
        ctx.flush();
        ctx.close();
        for (HostInfo connectionInfo : HOSTS) {
            // Configure the client.
            EventLoopGroup group = new NioEventLoopGroup();
            try {
                Bootstrap b = new Bootstrap();
                b.group(group)
                        .channel(NioSocketChannel.class)
                        .option(ChannelOption.TCP_NODELAY, true)
                        .handler(new ChannelInitializer<SocketChannel>() {
                            @Override
                            public void initChannel(SocketChannel ch) throws Exception {
                                ChannelPipeline p = ch.pipeline();
                                //p.addLast(new LoggingHandler(LogLevel.INFO));
                                p.addLast(new MultiplierClientHandler(buf.copy()));
                            }
                        });
                // Start the client.
                ChannelFuture f = b.connect(connectionInfo.getHost(), connectionInfo.getPort());
                f.addListener((ChannelFutureListener) (ChannelFuture future) -> {
                    if (future.isSuccess()) {
                        // connection complete start to read first data
                        LOG.log(Level.INFO, "Connected to {0}:{1} successfully.",
                                new Object[]{connectionInfo.getHost(), connectionInfo.getPort().toString()});
                    } else {
                        // Close the connection if the connection attempt has failed.
                        LOG.log(Level.WARNING, "Connection problem to {0}:{1}.",
                                new Object[]{connectionInfo.getHost(), connectionInfo.getPort().toString()});
                    }
                });
                // Wait until the connection is closed.
                f.channel().closeFuture().sync();
            } finally {
                // Shut down the event loop to terminate all threads.
                group.shutdownGracefully();
            }
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}