2.Netty服务端启动

所有 Netty 服务端的启动类都可以采用如下代码结构进行开发。简单梳理一下流程：首先创建引导器；然后配置线程模型，通过引导器绑定业务逻辑处理器，并配置一些网络参数；最后绑定端口，就可以完成服务器的启动了。

public class HttpServer {
    public void start(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .localAddress(new InetSocketAddress(port))
                    .childHandler(new ChannelInitializer() {
                        @Override
                        public void initChannel(SocketChannel ch) {
                            ch.pipeline()
                                    .addLast("codec", new HttpServerCodec())                  // HTTP 编解码
                                    .addLast("compressor", new HttpContentCompressor())       // HttpContent 压缩
                                    .addLast("aggregator", new HttpObjectAggregator(65536))   // HTTP 消息聚合
                                    .addLast("handler", new HttpServerHandler());             // 自定义业务逻辑处理器
                        }
                    })
                    .childOption(ChannelOption.SO_KEEPALIVE, true);
            ChannelFuture f = b.bind().sync();
            System.out.println("Http Server started， Listening on " + port);
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        new HttpServer().start(8088);
    }
}

public class HttpServerHandler extends SimpleChannelInboundHandler {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest msg) {
        String content = String.format("Receive http request, uri: %s, method: %s, content: %s%n", msg.uri(), msg.method(), msg.content().toString(CharsetUtil.UTF_8));
        FullHttpResponse response = new DefaultFullHttpResponse(
                HttpVersion.HTTP_1_1,
                HttpResponseStatus.OK,
                Unpooled.wrappedBuffer(content.getBytes()));
        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }
}

Q1:服务端的Socket在哪里初始化？
Q2:在哪里accpet连接？

1.bind() ----用户代码入口
2.initAndRegister() ---- 初始化并注册
3.new Channel() -----创建服务端Channel

NioServerSocketChannel:
反射创建服务端Channel
1.new Socket() ----通过jdk来创建底层jdk channel
2.NioServerSocketChannelConfig ----- tcp参数配置类
3.AbstractNioChannel()
configureBlocking(false) ------ 阻塞模式
AbstractChannel() -----创建id,unsafe,pipeline

init() — 初始化入口
set ChannelOptions, ChannelAttrs
set ChildOptions,ChildAttrs
config handler 配置服务端pipeline
add ServerBootstrapAcceptor 添加连接器

AbstractChannel.register(channel)[入口]
this.eventLoop = eventLoop[绑定线程]
register0()[实际注册]
doRegister()[调用jdk底层注册]
invokeHandlerAddedIfNeeded()
fireChannelRegistered[传播时间]

AbstractUnsafe.bind()[入口]
doBind()
javaChannel().bind()[jdk底层绑定]
pipeline.fireChannelActive()[传播事件]
HeadContext.readIfIsAutoRead()