Designing an event mechanism where an entity can be both listener (for some events) as well as generator (for some events) in C++

I am trying to create a basic design in c++ for an event mechanism which could have multiple event generators and listeners. The caveat here is that an object can behave as a listener (for some events) and a generator (for some other events). I am having a hard time figuring out the correct design for the same. Any suggestions please..