RE: How to send data from client to server?

Petter Myhre — Wed, 08 Oct 2014 07:07:00 GMT

The GATT client receives that data through an ATT Handle Value Notification, please see this MSC. See Bluetooth Specification 4.1, Vol. 3, Part G, Section 4.10, for details.
The GATT client "sends" data to the GATT server using a write procedure, please see this MSC. See Bluetooth Specification 4.1, Vol. 3, Part G, Section 4.9, for details. The GATT server receives the data, and sends a BLE_GATTS_EVT_WRITE event to the application, please see this MSC.
In a connection, all packets will be acknowledged in the link layer. So that part is reliable, but you have to use the remaining layers (ATT, GATT and application) in the correct way as well.

This question may also be helpful, explaining application level acknowledgement. Remember to vote on the question and the answer, if you find them useful.

Bluetooth Specification 4.1