How do I make a GATT server connect to a specific clients(without pairing mechanism)?

[Rifat Mahmud]

How do I make sure, the GATT server running on the BLE peripheral client connects only to a specific app based central/GATT client app, which has been authenticated via web? In other words, how Estimote allows its BLEs to connect only to its specific app.

[Anders Strand]

You can set up a pairing with a static passkey. This key will be constricted to 6 digits. Alternatively you can do this authentication through a GATT service. Then you can implement a more complex algorithm or scheme. (Btw, most peripheral devices are GATT servers, your phone will most likely be the GATT client).