Netty剖析之NIO群聊系统

秒速五厘米 2023-07-03 03:29 11阅读 0赞

### 前言 ###

在前面我们详细讲解了BIO、NIO，本次我们将使用NIO来完成一个群聊系统，实现服务器端和客户端之间的数据简单通讯（非阻塞）;

群聊系统基本要求：

*  服务器端可监测客户端上线、离线、并转发客户端消息；
 *  客户端可群发消息给其它用户，也可接收其它客户发送的消息；

### 代码示例 ###

服务端：

public class GroupChatServer {
    
        private Selector selector;
        private ServerSocketChannel serverSocketChannel;
    
        public GroupChatServer() {
        }
    
        public GroupChatServer(String host, int port) {
            try {
                // 创建选择器
                selector = Selector.open();
                // 创建ServerSocketChannel
                serverSocketChannel = ServerSocketChannel.open();
                // 绑定端口
                serverSocketChannel.socket().bind(new InetSocketAddress(host, port));
                // 设置非阻塞
                serverSocketChannel.configureBlocking(false);
                // 将ServerSocketChannel注册到selector
                serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
        public void listen() throws Exception {
            while (true) {
                if (selector.select() > 0) { // 监控是否有事件发生
                    // 获取有事件发生的SelectionKey
                    Set<SelectionKey> selectionKeySet = selector.selectedKeys();
                    Iterator<SelectionKey> selectionKeyIterator = selectionKeySet.iterator();
                    while (selectionKeyIterator.hasNext()) {
                        SelectionKey selectionKey = selectionKeyIterator.next();
                        if (selectionKey.isAcceptable()) { // 连接事件
                            SocketChannel socketChannel = serverSocketChannel.accept();
                            socketChannel.configureBlocking(false);
    
                            // 注册到selector
                            socketChannel.register(selector, SelectionKey.OP_READ);
    
                            System.out.println(socketChannel.getRemoteAddress() + "上线啦~");
                        } else if (selectionKey.isReadable()) { // 读取事件
                            // 反向获取Channel
                            SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
                            // 创建buffer
                            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
    
                            try {
                                if (socketChannel.read(byteBuffer) > 0) {
                                    // 读取到的消息
                                    String msg = new String(byteBuffer.array());
                                    System.out.println("接收到[" + socketChannel.getRemoteAddress() + "]发送的消息：" + msg);
    
                                    // 群发消息
                                    this.sendMsgToOtherClient(msg, socketChannel);
                                }
                            } catch (IOException e) {
                                System.out.println(socketChannel.getRemoteAddress() + "离线啦~");
                                selectionKey.channel(); // 取消此通道注册
                                socketChannel.close(); // 关闭此通道
                            }
                        }
                        selectionKeyIterator.remove();
                    }
                }
            }
        }
    
        /**
         * 转发消息给其它通道
         *
         * @param msg  转发的消息
         * @param self 当前通道，也就是群发排除的通道
         * @throws IOException
         */
        private void sendMsgToOtherClient(String msg, SocketChannel self) throws IOException {
            // 向其它客户端群发消息
            System.out.println("服务端开始转发消息。。。");
    
            // 获取所有注册到selector上的SocketChannel
            Set<SelectionKey> keySet = selector.keys();
            for (SelectionKey key : keySet) {
                Channel keyChannel = key.channel();
                // 群发时排除自己
                if (keyChannel instanceof SocketChannel && keyChannel != self) {
                    SocketChannel targetChannel = (SocketChannel) keyChannel;
    
                    // 将读取到的消息写入到SocketChannel
                    targetChannel.write(ByteBuffer.wrap(msg.getBytes()));
                }
            }
        }
    
        public static void main(String[] args) throws Exception {
            new GroupChatServer("127.0.0.1", 8899).listen();
        }
    }

客户端：

public class GroupChatClient {
    
        private Selector selector;
        private SocketChannel socketChannel;
        private String clientName;
    
        public GroupChatClient() {
        }
    
        public GroupChatClient(String serverHost, int serverPort) {
            try {
                // 创建一个selector
                selector = Selector.open();
                // 连接服务端
                socketChannel = SocketChannel.open(new InetSocketAddress(serverHost, serverPort));
                // 设置非阻塞
                socketChannel.configureBlocking(false);
                // 将客户端通道注册到selector
                socketChannel.register(selector, SelectionKey.OP_READ);
    
                clientName = socketChannel.getLocalAddress().toString().substring(1);
                System.out.println(clientName + "准备就绪~");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
        /**
         * 发送消息
         *
         * @param msg 消息
         * @throws IOException
         */
        public void sendMsg(String msg) throws IOException {
            msg = clientName + "说 ：" + msg;
            socketChannel.write(ByteBuffer.wrap(msg.getBytes()));
        }
    
        /**
         * 读取消息
         */
        public void readMsg() throws IOException {
            if (selector.select() > 0) { // 有事件发生的通道
                Set<SelectionKey> selectionKeySet = selector.selectedKeys();
                Iterator<SelectionKey> selectionKeyIterator = selectionKeySet.iterator();
                while (selectionKeyIterator.hasNext()) {
                    SelectionKey selectionKey = selectionKeyIterator.next();
                    if (selectionKey.isReadable()) { // 读取事件
                        // 反向获取channel
                        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
                        // 创建一个buffer
                        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
                        // 读取消息
                        socketChannel.read(byteBuffer);
    
                        System.out.println("收到一条消息：" + new String(byteBuffer.array()));
                    }
    
                    selectionKeyIterator.remove();
                }
            }
        }
    
        public static void main(String[] args) throws Exception {
            GroupChatClient groupChatClient = new GroupChatClient("127.0.0.1", 8899);
    
            // 独立一个线程进行消息读取
            new Thread(new Runnable() {
                @Override
                public void run() {
                    while (true) {
                        try {
                            groupChatClient.readMsg();
    
                            Thread.currentThread().sleep(2000);
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
            }).start();
    
            Scanner scanner = new Scanner(System.in);
            while (scanner.hasNextLine()) {
                // 获取控制台输入
                String inputMsg = scanner.nextLine();
                groupChatClient.sendMsg(inputMsg);
            }
        }
    }

通讯演示：  
服务端：

/127.0.0.1:10481上线啦~
    /127.0.0.1:10499上线啦~
    /127.0.0.1:10537上线啦~
    接收到[/127.0.0.1:10481]发送的消息：127.0.0.1:10481说 ：client1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    服务端开始转发消息。。。
    接收到[/127.0.0.1:10499]发送的消息：127.0.0.1:10499说 ：client2                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    服务端开始转发消息。。。
    接收到[/127.0.0.1:10537]发送的消息：127.0.0.1:10537说 ：client3                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    服务端开始转发消息。。。
    /127.0.0.1:10481离线啦~
    /127.0.0.1:10499离线啦~
    /127.0.0.1:10537离线啦~

client1：

127.0.0.1:10481准备就绪~
    client1
    收到一条消息：127.0.0.1:10499说 ：client2                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    收到一条消息：127.0.0.1:10537说 ：client3

client2：

127.0.0.1:10499准备就绪~
    收到一条消息：127.0.0.1:10481说 ：client1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    client2
    收到一条消息：127.0.0.1:10537说 ：client3

client3：

127.0.0.1:10537准备就绪~
    收到一条消息：127.0.0.1:10481说 ：client1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    收到一条消息：127.0.0.1:10499说 ：client2                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    client3