Netty  异步的 基于事件驱动的网络编程框架

BIO 
NIO  non-blocking IO 

Netty 中的 I/O 操作是异步的（Bind、Connect、Write等操作 ），会立刻返回一个 ChannelFuture

Future-Listener 机制

future 和 callback

sync 	阻塞等待结果返回
isDone  判断当前操作是否完成
isSuccess  
getCause  获取已完成的当前操作失败原因
isCancelled  
addListener  注册监听器


 ChannelFuture channelFuture = serverBootstrap.bind(8888).sync();
channelFuture.addListener(new ChannelFutureListener() {
        @Override
        public void operationComplete(ChannelFuture channelFuture) throws Exception {
            if (channelFuture.isSuccess()){
                System.out.println("Server bind success");
            }else {
                System.out.println("Server bind failed");
            }
            }
        });

 @Override
    public void channelActive(ChannelHandlerContext channelHandlerContext) throws Exception{
        ChannelFuture channelFuture = channelHandlerContext.writeAndFlush(Unpooled.copiedBuffer("hello，netty", CharsetUtil.UTF_8));
        channelFuture.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture channelFuture) throws Exception {
                if (channelFuture.isSuccess()){
                    System.out.println("Client send success");
                }else {
                    System.out.println("Client send failed");
                }
            }
        });
    }




 netty ChannelFuture 实例  
 netty中的future和promise