NIO实现

服务端实现：

public static void main(String[] args) {
        int port = 7236;
        //NIO多路复用
        //创建线程池
        ThreadPoolExecutor threadPool = new ThreadPoolExecutor(4, 4, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());
        threadPool.execute(new Runnable() {
            @Override
            public void run() {
                try (Selector selector = Selector.open();
                     //ServerSocketChannel构造方法使用Protected进行修饰的
                     ServerSocketChannel serverSocketChannel = ServerSocketChannel.open()) {
                    //绑定服务
                    serverSocketChannel.bind(new InetSocketAddress(InetAddress.getLocalHost(), port));
                    /*  设置 SocketChannel 为非阻塞模式
                        设置之后，就可以在异步模式下调用connect(), read() 和write()了
                     */
                    serverSocketChannel.configureBlocking(false);
                    //
                    serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
                    while (true) {
                        selector.select();//阻塞等待就绪的Channel
                        //
                        Set<SelectionKey> selectionKeys = selector.selectedKeys();
                        Iterator<SelectionKey> iterator = selectionKeys.iterator();
                        while (iterator.hasNext()) {
                            SelectionKey key = iterator.next();
                            try (SocketChannel channel = ((ServerSocketChannel) key.channel()).accept();) {
                                channel.write(Charset.defaultCharset().encode("你好，世界-zzd"));
                            }
                            iterator.remove();
                        }
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });

    }

客户端实现：

public static void main(String[] args) {
        int port = 7236;
        //Socket客户端（接收信息并打印）
        try(Socket socket = new Socket(InetAddress.getLocalHost(), port)){
            BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            reader.lines().forEach(s-> System.out.println("客户端：" + s));
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

调用过程讲解：

• 首先，通过Selector.open()创建一个Selector,作为类似调度员的角色
• 然后，创建一个ServerSocketChannel,并且向Selector注册，通过指定SelectionKey.OP_ACCEPT，告诉调度员，它关注的是新建立的连接请求
• 为甚我们要明确配置非阻塞模式？这是因为阻塞模式下，注册操作是不允许的，会抛出IllegalBlockingModeException异常
• Selector阻塞在select操作，当有Channel发生接入请求，就会被唤醒