Connect and Write Byte Data On Raspberry PI-3.0(RP)

We are using Raspberry PI-3.0(RP) as our bluetooth server and iPhone app as client. We need to use classic Bluetooth classes to communicate with RP to send small piece of data. The connection will hardly take 3 minutes to do their job from iPhone side.
Issue: when we redirect to bluetooth settings and try to connect RP, iPhone gets disconnected immediately and we can't get the read wride channels.

Can you guys please help us to achieve this functionality?
Connect and Write Byte Data On Raspberry PI-3.0(RP)
 
 
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