根据进程ID连接JMX，代码测试

import sun.misc.VM;
import sun.misc.VMSupport;

import java.io.IOException;
import java.net.ServerSocket;

/**
 * Created by DUDU on 2018/6/12.
 */
public class Server {

    public static void main(String[] args) throws InterruptedException {
        try {
//            ServerSocket ss = new ServerSocket(21000);
//            String addr = System.getProperty("com.sun.management.jmxremote.localConnectorAddress");
            String addr = (String) VMSupport.getAgentProperties().get("com.sun.management.jmxremote.localConnectorAddress");
            System.out.println("addr1:" + addr);
            if (addr == null) {
//                Thread.currentThread().getContextClassLoader().loadClass("");
//                Class.forName("sun.management.Agent");
                sun.management.Agent.premain("");
            }
            addr = (String) VMSupport.getAgentProperties().get("com.sun.management.jmxremote.localConnectorAddress");
            System.out.println(addr);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }

        Thread.sleep(50000000L);
    }

}

JVM在加载sun.management.Agent后，会监听一个地址，端口随机，我测试的时候是：
service:jmx:rmi://127.0.0.1/stub/rO0ABXNyAC5qYXZheC5tYW5hZ2VtZW50LnJlbW90ZS5ybWkuUk1JU2VydmVySW1wbF9TdHViAAAAAAAAAAICAAB4cgAaamF2YS5ybWkuc2VydmVyLlJlbW90ZVN0dWLp/tzJi+FlGgIAAHhyABxqYXZhLnJtaS5zZXJ2ZXIuUmVtb3RlT2JqZWN002G0kQxhMx4DAAB4cHc1AAtVbmljYXN0UmVmMgAACjEwLjEuNy4yMTcAAMptncwWe1hOy/PhQ2ADAAABY/0c42+AAQB4

注意这时候的IP和端口实际是在后面加密的串里面，前面那个127.0.0.1是骗人的

所以客户端连接程序为：

JMXServiceURL jmxUrl = new JMXServiceURL("service:jmx:rmi://127.0.0.1/stub/rO0ABXNyAC5qYXZheC5tYW5hZ2VtZW50LnJlbW90ZS5ybWkuUk1JU2VydmVySW1wbF9TdHViAAAAAAAAAAICAAB4cgAaamF2YS5ybWkuc2VydmVyLlJlbW90ZVN0dWLp/tzJi+FlGgIAAHhyABxqYXZhLnJtaS5zZXJ2ZXIuUmVtb3RlT2JqZWN002G0kQxhMx4DAAB4cHc1AAtVbmljYXN0UmVmMgAACjEwLjEuNy4yMTcAAMptncwWe1hOy/PhQ2ADAAABY/0c42+AAQB4");
        JMXConnector jmxc = JMXConnectorFactory.connect(jmxUrl);