I want to send data from iPhone to a bluetooth device which get discovered and connects. I am referring this tutorial to connect.
I am not able to send data to external bluetooth device which is connected as we do with External Accessory framework.
I am using iPhone5 as it has Bluetooth 4.0
In Core Bluetooth you need to use the characteristics for communication. There is no standard stream based API like in the External Accessory Framework and I don't know of any open source libraries that implement something like that.
Basic operation
Peripheral -> Central:
Central -> Peripheral:
The actual speed you can achieve depends on various factors. With indications the data is never lost (like TCP) but notifications don't have such guarantees (like UDP).
More info
I suggest you check out the official Core Bluetooth Programming Guide and concentrate on the
sections. But better would be studying the whole guide as is. For a working example, check out the BTLE Transfer example from Apple, as well.