Why Netty is awesome.

App.java

package com.md_5.jcaptive;

import io.netty.bootstrap.Bootstrap;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundMessageHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.socket.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.HttpClientCodec;
import io.netty.handler.codec.http.HttpRequest;
import io.netty.handler.codec.http.HttpResponse;
import io.netty.handler.codec.http.HttpServerCodec;

public class App {

    public static void main(String[] args) {
        new ServerBootstrap().channel(new NioServerSocketChannel()).childHandler(new ChannelInitializer() {
            @Override
            public void initChannel(Channel ch) throws Exception {
                ch.pipeline().addLast(new HttpServerCodec(), new ChannelInboundMessageHandlerAdapter<HttpRequest>() {
                    @Override
                    public void messageReceived(final ChannelHandlerContext client, final HttpRequest request) throws Exception {
                        String[] header = request.getHeader("Host").split(":", 2);
                        new Bootstrap().channel(new NioSocketChannel()).group(new NioEventLoopGroup()).remoteAddress(header[0], header.length == 2 ? Integer.parseInt(header[1]) : 80).handler(new ChannelInitializer() {
                            @Override
                            public void initChannel(Channel ch) throws Exception {
                                ch.pipeline().addLast(new HttpClientCodec(), new ChannelInboundMessageHandlerAdapter<HttpResponse>() {
                                    @Override
                                    public void messageReceived(ChannelHandlerContext server, HttpResponse response) throws Exception {
                                        client.write(response).addListener(ChannelFutureListener.CLOSE);
                                    }
                                });
                            }
                        }).connect().addListener(new ChannelFutureListener() {
                            public void operationComplete(ChannelFuture future) throws Exception {
                                future.channel().write(request);
                            }
                        });
                    }
                });
            }
        }).group(new NioEventLoopGroup()).localAddress(7777).bind();
    }
}

The code like a JS callback hell...