Bluetooth: Connecting without UUID

Question

Yesterday i learned that i need to know the UUID of the Device which i want to connect with but that leaded to some questions i could not answer myself and i could not found it in the web either.

If i connect two devices which are running the same Software or App or anything else it is easy to hardcode those UUID's but what if it is not the same Software or the same App? For example if i transfer contact data from my Android Phone to a friends Apple iPhone, how could my Android Phone know the UUID of the iPhone?

Another example would be my Bluetooth-Headphones. I never installed any Software or any App on my Device but after the Bluetooth-Pairing my Headphones are working. How could my Headphones know the UUID of my Android phone?

Answer 1

Okay, got it: Service Discovery Protocol (SDP)

There are several fix UUID's that can be used for different services. So what i have to do for my purpose is just to use my own UUID on each device.