How to keep subscriber in the "waiting" state rospy.wait_for_message()

I'd like my C++ client subscriber `wait for topic`  just like in ROS:  
```
rospy.wait_for_message('/topic', String)
```  
Any ideas how to make a thread with a goal?  

Checking for [wss_examples.cpp](https://gitlab.com/eidheim/Simple-WebSocket-Server/-/blob/master/wss_examples.cpp) didn't help..