java socket长连接心跳检测代码

下面是一个简单的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 SocketClient {

    public static void main(String[] args) {
        String host = "localhost";
        int port = 8080;
        try {
            Socket socket = new Socket(host, port);
            InputStream in = socket.getInputStream();
            OutputStream out = socket.getOutputStream();
            while (true) {
                // 发送心跳包
                out.write("ping".getBytes());
                out.flush();
                // 等待服务器响应
                byte[] buffer = new byte[1024];
                int len = in.read(buffer);
                if (len == -1) {
                    System.out.println("Server closed connection.");
                    break;
                }
                String response = new String(buffer, 0, len);
                if ("pong".equals(response)) {
                    System.out.println("Received pong from server.");
                } else {
                    System.out.println("Received unknown response from server: " + response);
                }
                // 等待一段时间再次发送心跳包
                Thread.sleep(5000);
            }
        } catch (IOException e) {
            System.out.println("Error connecting to server: " + e.getMessage());
        } catch (InterruptedException e) {
            System.out.println("InterruptedException occurred: " + e.getMessage());
        }
    }
}

在这个示例中，客户端向服务器发送一个字符串"ping"作为心跳包，然后等待服务器响应。如果服务器响应了"pong"，客户端会打印出"Received pong from server."，否则会打印出"Received unknown response from server:" 加上收到的响应内容。在等待一段时间（这里是5000毫秒）之后，客户端会再次发送心跳包。如果服务器关闭了连接，客户端会退出循环并打印出"Server closed connection."。