I'll keep it short.
Using ZMQ to communicate between Python(server) and C ( client ). ( made a game ) 
The goal is to get the server side running only when the client connects.
Is there a way to detect something in ZeroMQ to start the program?
Q : "Is there a way to detect something in ZeroMQ to start the program?"

I'll keep it short.
Yes, there is.

 read all details in the published API about using the socket_monitor() for handling this and similar events. Definitely doable & easy to integrateYou will soon fall in love with the ZeroMQ's smart tools & the designed-in art of the Zen of ZeroDefinitely a good pick :o)
Detecting a "join" ZMQ