[API] NOTIFY message: when and how?

I read the documentation that after “joining” the network (I don’t understand this either, what’s the sign of successful joining? Is a reply to my broadcast enough?), the bulb will send NOTIFY message periodically in fixed interval, but no numbers specified and how it will be done (UDP? TCP? Something else?).

The discover mechanism is almost clear but I eventually need to figure out myself that both broadcast and response are UDP, while the command-response is clearly TCP. Only notify is left unclear because both listening to TCP and UDP at the broadcast address and port, I never get any of those notify after waiting for several minutes. Instead, I have to do polling myself on every interval I specify. I prefer push instead of pull whenever possible, but I have difficulty receiving it at the moment.