Java Socket通信中怎样进行心跳检测

在Java Socket通信中，进行心跳检测的目的是为了保持连接的活跃状态，防止因为长时间不通信导致的连接被客户端或服务器端主动关闭。下面是一个简单的心跳检测示例：

1. 服务器端：

import java.io.*; import java.net.*; import java.util.concurrent.*;  public class Server {     public static void main(String[] args) throws IOException, InterruptedException {         int port = 12345;         ExecutorService executorService = Executors.newFixedThreadPool(10);         ServerSocket serverSocket = new ServerSocket(port);          while (true) {             Socket clientSocket = serverSocket.accept();             executorService.submit(() -> handleClient(clientSocket));         }     }      private static void handleClient(Socket clientSocket) {         try {             InputStream inputStream = clientSocket.getInputStream();             OutputStream outputStream = clientSocket.getOutputStream();              BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));             PrintWriter writer = new PrintWriter(outputStream, true);              String heartBeatMessage = "HEARTBEAT";             while (true) {                 // 发送心跳包                 writer.println(heartBeatMessage);                 Thread.sleep(5000); // 每5秒发送一次心跳包                  // 读取客户端返回的消息                 String message = reader.readLine();                 if (message != null && message.equals(heartBeatMessage)) {                     // 收到客户端的心跳包，回应一个确认消息                     writer.println("HEARTBEAT_ACK");                 } else {                     // 没有收到心跳包，关闭连接                     break;                 }             }         } catch (IOException | InterruptedException e) {             e.printStackTrace();         } finally {             try {                 clientSocket.close();             } catch (IOException e) {                 e.printStackTrace();             }         }     } } 

2. 客户端：

import java.io.*; import java.net.*; import java.util.concurrent.*;  public class Client {     public static void main(String[] args) throws IOException, InterruptedException {         String serverAddress = "localhost";         int port = 12345;         Socket socket = new Socket(serverAddress, port);         ExecutorService executorService = Executors.newFixedThreadPool(10);          // 启动一个线程定期发送心跳包         executorService.submit(() -> sendHeartBeat(socket));          BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));         String message;         while ((message = reader.readLine()) != null) {             System.out.println("Received from server: " + message);             if (message.equals("HEARTBEAT_ACK")) {                 // 收到服务器的确认消息，继续发送心跳包                 sendHeartBeat(socket);             }         }     }      private static void sendHeartBeat(Socket socket) throws IOException, InterruptedException {         OutputStream outputStream = socket.getOutputStream();         PrintWriter writer = new PrintWriter(outputStream, true);         String heartBeatMessage = "HEARTBEAT";         while (true) {             // 发送心跳包             writer.println(heartBeatMessage);             Thread.sleep(5000); // 每5秒发送一次心跳包         }     } } 

在这个示例中，服务器端和客户端都会定期发送心跳包，以保持连接的活跃状态。如果一方在一段时间内没有收到心跳包，它会认为连接已经断开，并关闭连接。