1.引入gradle依赖，当然你也可以引用pom的Netty依赖，

dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.12'
    // https://mvnrepository.com/artifact/io.netty/netty-all
    compile group: 'io.netty', name: 'netty-all', version: '4.1.10.Final'
}

2.主程序

package com.liyuanfeng.netty.firstexample;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
public class TestServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup, workGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new TestServerInitializer());
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }
    }
}

3.初始化器

package com.liyuanfeng.netty.firstexample;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpServerCodec;
public class TestServerInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast("httpServerCodec", new HttpServerCodec());
        pipeline.addLast("testHttpServereHandler", new TestHttpServerHandler());
    }
}

4.处理请求的Handler

public class TestHttpServerHandler extends SimpleChannelInboundHandler<HttpObject> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
        if (msg instanceof HttpRequest) {
            ByteBuf content = Unpooled.copiedBuffer("Hello World", CharsetUtil.UTF_8);
            FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, content);
            response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain");
            response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes());
            ctx.writeAndFlush(response);
        }
    }
}

5.结果

image.png