First of all:
Client: API interface to retrieve data from remote device
Server: API interface to hold data for retrieval from remote device
Central: Device that initiates and controls BLE connection
Peripheral: Device that waits for a BLE connection
In order to pair two devices together, they must first connect together, then initiate and accept the pairing (central initiates, peripheral accepts).
Once they are paired, if the central connects to the peripheral, then it will reuse the connection data and skip the whole verification process by using the stored data from the previous connection (essentially).
There is an API function that is called to pair to a connected device by the API software:
You would need to write the software in such a way as to find, connect to, then pair with the server you want the client to Pair/Bond with.
Pairing: Connection is encrypted
Bonding: Connection is stored for future use/connections