public class SocketNioTcpServer {
    private static List<SocketChannel> listSocketChannel = new ArrayList<>();
    private static ByteBuffer byteBuffer = ByteBuffer.allocate(512);
    public static void main(String[] args) {
        try {
            // 1.創(chuàng)建一個ServerSocketChannel
            ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
            // 2. 綁定地址
            ServerSocketChannel bind = serverSocketChannel.bind(new InetSocketAddress(8080));
            serverSocketChannel.configureBlocking(false);
            while (true) {
                SocketChannel socketChannel = serverSocketChannel.accept();
                if (socketChannel != null) {
                    socketChannel.configureBlocking(false);
                    listSocketChannel.add(socketChannel);
                }
                for (SocketChannel scl : listSocketChannel) {
                    try {
                        int read = scl.read(byteBuffer);
                        if (read > 0) {
                            byteBuffer.flip();
                            Charset charset = Charset.forName("UTF-8");
                            String receiveText = charset.newDecoder().decode
                                    (byteBuffer.asReadOnlyBuffer()).toString();
                            System.out.println("receiveText:" + receiveText);
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public class NIOServer {
    /**
     * 創(chuàng)建一個選擇器
     */
    private Selector selector;
    public void initServer(int port) throws IOException {
        // 獲得一個ServerSocketChannel通道
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        // 設置通道為非阻塞
        serverSocketChannel.configureBlocking(false);
        // 將該通道對應的ServerSocket綁定到port端口
        serverSocketChannel.bind(new InetSocketAddress(port));
        // 獲得一個通道管理器
        this.selector = Selector.open();
        // 將通道管理器和該通道綁定，并為該通道注冊SelectionKey.OP_ACCEPT事件,注冊該事件后，
        // 當該事件到達時，selector.select()會返回，如果該事件沒到達selector.select()會一直阻塞。
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
    }
    public void listen() throws IOException {
        System.out.println("服務端啟動成功！");
        // 輪詢訪問selector
        while (true) {
            // 當注冊的事件到達時，方法返回；否則,該方法會一直阻塞
            int select = selector.select();
            if (select == 0) {
                continue;
            }
            // 獲得selector中選中的項的迭代器，選中的項為注冊的事件
            Iterator<SelectionKey> ite = this.selector.selectedKeys().iterator();
            while (ite.hasNext()) {
                SelectionKey key = (SelectionKey) ite.next();
                // 刪除已選的key,以防重復處理
                ite.remove();

                if (key.isAcceptable()) {// 客戶端請求連接事件
                    ServerSocketChannel server = (ServerSocketChannel) key.channel();
                    // 獲得和客戶端連接的通道
                    SocketChannel channel = server.accept();
                    // 設置成非阻塞
                    channel.configureBlocking(false);
                    // 在和客戶端連接成功之后，為了可以接收到客戶端的信息，需要給通道設置讀的權限。
                    channel.register(this.selector, SelectionKey.OP_READ);

                } else if (key.isReadable()) {// 獲得了可讀的事件
                    read(key);
                }

            }

        }
    }
    public void read(SelectionKey key) throws IOException {
        // 服務器可讀取消息:得到事件發(fā)生的Socket通道
        SocketChannel channel = (SocketChannel) key.channel();
        // 創(chuàng)建讀取的緩沖區(qū)
        ByteBuffer buffer = ByteBuffer.allocate(512);
        channel.read(buffer);
        byte[] data = buffer.array();
        String msg = new String(data).trim();
        System.out.println("服務端收到信息：" + msg);
        ByteBuffer outBuffer = ByteBuffer.wrap(msg.getBytes("utf-8"));
        channel.write(outBuffer);// 將消息回送給客戶端
    }
    public static void main(String[] args) throws IOException {
        NIOServer server = new NIOServer();
        server.initServer(8000);
        server.listen();
    }
}