Java socket长连接心跳检测代码

以下是一个简单的Java socket长连接心跳检测代码示例：

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;

public class HeartbeatClient {
    private static final int SERVER_PORT = 8888;
    private static final String SERVER_IP = "127.0.0.1";
    private static final long HEARTBEAT_INTERVAL = 5000; // 心跳间隔时间，单位毫秒

    public static void main(String[] args) {
        Socket socket = null;
        InputStream in = null;
        OutputStream out = null;
        try {
            socket = new Socket(SERVER_IP, SERVER_PORT);
            in = socket.getInputStream();
            out = socket.getOutputStream();
            // 发送心跳包
            new Thread(new HeartbeatThread(out)).start();
            byte[] buffer = new byte[1024];
            int len;
            while ((len = in.read(buffer)) != -1) {
                String message = new String(buffer, 0, len);
                System.out.println("收到服务器的消息：" + message);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
                if (socket != null) {
                    socket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private static class HeartbeatThread implements Runnable {
        private OutputStream out;

        public HeartbeatThread(OutputStream out) {
            this.out = out;
        }

        @Override
        public void run() {
            while (true) {
                try {
                    Thread.sleep(HEARTBEAT_INTERVAL);
                    out.write("heartbeat".getBytes());
                    out.flush();
                    System.out.println("发送心跳包");
                } catch (InterruptedException | IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

这个示例中，我们在客户端和服务器之间建立了一个长连接，并且每隔一段时间就发送一个心跳包到服务器，以确保连接不会因为长时间没有数据交换而断开。在线程中，我们使用了`Thread.sleep()`来实现心跳包发送的定时器功能。当连接断开或者发送心跳包失败时，我们可以在`catch`块中重新连接或者做其他处理。