Main.java

package http;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.compression.CompressionOptions;
import io.netty.handler.codec.http.*;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

import static io.netty.handler.codec.http.HttpHeaderNames.CONNECTION;
import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_LENGTH;
import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_TYPE;
import static io.netty.handler.codec.http.HttpHeaderValues.CLOSE;
import static io.netty.handler.codec.http.HttpHeaderValues.KEEP_ALIVE;
import static io.netty.handler.codec.http.HttpHeaderValues.TEXT_PLAIN;
import static io.netty.handler.codec.http.HttpResponseStatus.OK;

public class Main {

    public static final int PORT = 8080;

    public static void main(String[] args) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.option(ChannelOption.SO_BACKLOG, 1024);
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline()
                                    .addLast(new HttpServerCodec())
                                    .addLast(new HttpContentCompressor((CompressionOptions[]) null))
                                    .addLast(new HttpServerExpectContinueHandler())
                                    .addLast(new HttpHelloWorldServerHandler());
                        }
                    });

            Channel ch = b.bind(PORT).sync().channel();

            System.out.println("http://localhost:" + PORT + "/");

            ch.closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static class HttpHelloWorldServerHandler extends SimpleChannelInboundHandler<HttpRequest> {

        @Override
        protected void channelRead0(ChannelHandlerContext ctx, HttpRequest req) throws Exception {
            boolean keepAlive = HttpUtil.isKeepAlive(req);
            FullHttpResponse response = new DefaultFullHttpResponse(req.protocolVersion(), OK,
                    Unpooled.wrappedBuffer((req.method() + " " + PORT + " " + req.uri()).getBytes()));
            response.headers()
                    .set(CONTENT_TYPE, TEXT_PLAIN)
                    .setInt(CONTENT_LENGTH, response.content().readableBytes());

            if (keepAlive) {
                if (!req.protocolVersion().isKeepAliveDefault()) {
                    response.headers().set(CONNECTION, KEEP_ALIVE);
                }
            } else {
                response.headers().set(CONNECTION, CLOSE);
            }

            ChannelFuture f = ctx.write(response);

            if (!keepAlive) {
                f.addListener(ChannelFutureListener.CLOSE);
            }
            ctx.flush();
        }

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

    }

}