java socket长连接实现心跳检测代码

下面是一个基于 Java Socket 的长连接实现心跳检测的代码示例：

客户端代码：

public class Client {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket("127.0.0.1", 8888);
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
        // 发送心跳包
        ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);
        executorService.scheduleAtFixedRate(() -> {
            out.println("ping");
        }, 0, 3, TimeUnit.SECONDS);
        // 接收消息
        String message;
        while ((message = in.readLine()) != null) {
            System.out.println(message);
        }
    }
}

服务端代码：

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8888);
        while (true) {
            Socket socket = serverSocket.accept();
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            // 接收心跳包
            ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);
            executorService.scheduleAtFixedRate(() -> {
                try {
                    String message = in.readLine();
                    if ("ping".equals(message)) {
                        out.println("pong");
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }, 0, 3, TimeUnit.SECONDS);
        }
    }
}

在客户端和服务端分别启动后，客户端会每隔 3 秒发送一个 "ping" 消息，服务端会每隔 3 秒接收客户端的消息并判断是否是心跳包，如果是则回复一个 "pong" 消息。这样就可以通过心跳检测来保持长连接的存活状态。