public class BioServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(9000);
        // 任務(wù)處理線程池
        ExecutorService pool = Executors.newFixedThreadPool(10);
        while (true) {
            System.out.println("server start");
            //阻塞方法等待客戶端連接
            Socket clientSocket = serverSocket.accept();
            System.out.println("new client");
            pool.execute(()->{
                handler(clientSocket);
            });
        }
    }
    private static void handler(Socket clientSocket) {
        try {
            byte[] bytes = new byte[1024];
            System.out.println("reading");
            //接收客戶端的數(shù)據(jù)，阻塞方法，沒有數(shù)據(jù)可讀時就阻塞
            int read = clientSocket.getInputStream().read(bytes);
            System.out.println("read over");
            if (read != -1) {
                System.out.println("received data：" + new String(bytes, 0, read));
            }
            clientSocket.getOutputStream().write("HelloClient".getBytes());
            clientSocket.getOutputStream().flush();
        } catch (Exception e) {
        }
    }
}

public class NioServer {
    public static void main(String[] args) throws IOException, InterruptedException {
        // 創(chuàng)建NIO ServerSocketChannel
        ServerSocketChannel serverSocket = ServerSocketChannel.open();
        serverSocket.socket().bind(new InetSocketAddress(9000));
        serverSocket.configureBlocking(false);
        // 打開Selector處理Channel，底層調(diào)用epoll_create
        Selector selector = Selector.open();
        // 把ServerSocketChannel注冊到selector上，并且selector對客戶端accept連接操作感興趣，底層調(diào)用epoll_ctl
        serverSocket.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("服務(wù)啟動成功");
        while (true) {
            // 阻塞等待需要處理的事件發(fā)生，即調(diào)用epoll_wait
            selector.select();
            // 獲取selector中注冊的全部事件的 SelectionKey 實例
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            // 遍歷SelectionKey對事件進行處理
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                // 如果是OP_ACCEPT事件，則進行連接獲取和事件注冊
                if (key.isAcceptable()) {
                    ServerSocketChannel server = (ServerSocketChannel) key.channel();
                    SocketChannel socketChannel = server.accept();
                    socketChannel.configureBlocking(false);
                    // 這里只注冊了讀事件，如果需要給客戶端發(fā)送數(shù)據(jù)可以注冊寫事件，底層調(diào)用epoll_ctl
                    socketChannel.register(selector, SelectionKey.OP_READ);
                    System.out.println("客戶端連接成功");
                } else if (key.isReadable()) {  // 如果是OP_READ事件，則進行讀取和打印
                    SocketChannel socketChannel = (SocketChannel) key.channel();
                    ByteBuffer byteBuffer = ByteBuffer.allocate(128);
                    int len = socketChannel.read(byteBuffer);
                    // 如果有數(shù)據(jù)，把數(shù)據(jù)打印出來
                    if (len > 0) {
                        System.out.println("接收到消息：" + new String(byteBuffer.array()));
                    } else if (len == -1) { // 如果客戶端斷開連接，關(guān)閉Socket
                        System.out.println("客戶端斷開連接");
                        socketChannel.close();
                    }
                }
                //從事件集合里刪除本次處理的key，防止下次select重復處理
                iterator.remove();
            }
        }
    }
}