Java NIO 编程 - 群聊系统

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public class GroupChatServer {
    // 定义属性
    private Selector selector;
    private ServerSocketChannel listenChannel;
    private static final int PORT = 6667;

    // 构造器
    // 初始化工作
    public GroupChatServer() {
        try {
            // 得到选择器
            selector = Selector.open();
            // ServerSocketChannel
            listenChannel = ServerSocketChannel.open();
            // 绑定端口
            listenChannel.socket().bind(new InetSocketAddress(PORT));
            // 设置非阻塞模式
            listenChannel.configureBlocking(false);
            // 将该 listenChannel 注册到 selector
            listenChannel.register(selector, SelectionKey.OP_ACCEPT);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 监听
    public void listen() {
        try {
            // 循环处理
            while (true) {
                int count = selector.select();
                if (count > 0) { // 有事件处理
                    // 遍历得到 selectionKey 集合
                    Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                    while (iterator.hasNext()) {
                        // 取出 selectionKey
                        SelectionKey key = iterator.next();
                        // 监听到 accept
                        if (key.isAcceptable()) {
                            SocketChannel sc = listenChannel.accept();
                            sc.configureBlocking(false);
                            // 将该 sc 注册到 selector
                            sc.register(selector, SelectionKey.OP_READ);
                            System.out.println(sc.getRemoteAddress() + " 上线");
                        }
                        if (key.isReadable()) { // 通道发生 read 事件，即通道是可读的状态
                            // 处理读的事件（专门写方法...）
                            readData(key);
                        }
                        // 当前的 key 删除，防止重复处理
                        iterator.remove();
                    }
                } else {
                    System.out.println("等待.....");
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 读取客户端消息
    private void readData(SelectionKey key) {
        // 定义一个 SocketChannel
        SocketChannel channel = null;
        try {
            // 得到 channel
            channel = (SocketChannel) key.channel();
            // 创建 buffer
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            int count = channel.read(buffer);
            // 根据 count 的值做处理
            if (count > 0) {
                // 把缓冲区的数据转成字符串
                String msg = new String(buffer.array());
                // 输出该消息
                System.out.println("from 客户端：" + msg);
                // 向其他客户端转发消息（专门写方法...）
                sendInfoToOtherClients(msg, channel);
            }
        } catch (IOException e) {
            try {
                System.out.println(channel.getRemoteAddress() + " 离线了...");
                // 取消注册
                key.cancel();
                // 关闭通道
                channel.close();
            } catch (IOException ioException) {
                ioException.printStackTrace();
            }
        }
    }

    // 转发消息给其他客户（通道）
    private void sendInfoToOtherClients(String msg, SocketChannel self) throws IOException {
        System.out.println("服务器转发消息中...");
        // 遍历所有注册到 selector 上的 SocketChannel，并排除 self
        for (SelectionKey key : selector.keys()) {
            // 通过 key 取出对应的 SocketChannel
            Channel targetChannel = key.channel();
            // 排除自己
            if (targetChannel instanceof SocketChannel && targetChannel != self) {
                // 转型
                SocketChannel dest = (SocketChannel) targetChannel;
                // 将 msg 存储到 buffer
                ByteBuffer buffer = ByteBuffer.wrap(msg.getBytes());
                // 将 buffer 的数据写入通道
                dest.write(buffer);
            }
        }
    }

    public static void main(String[] args) {
        // 创建服务器对象
        GroupChatServer groupChatServer = new GroupChatServer();
        groupChatServer.listen();
    }
}

public class GroupChatClient {
    private final Selector selector;
    private final SocketChannel socketChannel;
    private final String username;

    // 构造器，完成初始化
    public GroupChatClient() throws IOException {
        selector = Selector.open();
        // 连接服务器
        // 定义属性
        String HOST = "127.0.0.1";
        int PORT = 6667;
        socketChannel = SocketChannel.open(new InetSocketAddress(HOST, PORT));
        // 设置非阻塞
        socketChannel.configureBlocking(false);
        // 将 channel 注册到 selector
        socketChannel.register(selector, SelectionKey.OP_READ);
        // 得到 username
        username = socketChannel.getLocalAddress().toString().substring(1);
        System.out.println(username + " is ok...");
    }

    // 向服务器发送消息
    public void sendInfo(String info) {
        info = username + " 说：" + info;
        try {
            socketChannel.write(ByteBuffer.wrap(info.getBytes()));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 读取从服务器端回复的消息
    public void readInfo() {
        try {
            int readChannels = selector.select();
            if (readChannels > 0) { // 有可以用的通道
                Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                while (iterator.hasNext()) {
                    SelectionKey key = iterator.next();
                    if (key.isReadable()) {
                        // 得到相关的通道
                        SocketChannel sc = (SocketChannel) key.channel();
                        // 得到一个 Buffer
                        ByteBuffer buffer = ByteBuffer.allocate(1024);
                        // 读取
                        sc.read(buffer);
                        // 把读到的缓冲区的数据转换成字符串
                        String msg = new String(buffer.array());
                        System.out.println(msg.trim());
                    }
                }
                iterator.remove(); // 删除当前的 selectionKey, 防止重复操作
            }  // System.out.println("没有可用的通道...");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws IOException {
        // 启动客户端
        GroupChatClient chatClient = new GroupChatClient();
        // 启动一个线程, 每隔3秒，读取从服务器发送的数据
        new Thread(() -> {
            while (true) {
                chatClient.readInfo();
                try {
                    Thread.sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();

        // 发送数据给服务器端
        Scanner scanner = new Scanner(System.in);

        while (scanner.hasNextLine()) {
            String s = scanner.nextLine();
            chatClient.sendInfo(s);
        }

    }
}