While the GAP profile defines the low-level (advertising and connection) interactions of Bluetooth LE devices, the GATT profile defines the details on how the devices exchange data. The GATT is also the reference framework for all attribute-based profiles that define specific use cases, such as heart rate and blood pressure profiles.
As with the GAP profile, the GATT profile defines two roles. These roles are the client and the server. When you look at the diagram on how this works, the roles may seem a little odd at first; however, once we see how Bluetooth LE devices exchange data it will make more sense. The client role in the GATT profile corresponds to the master role in the GAP profile and the server ...
