iPhone corebluetooth central Manager send data to peripheral

Question

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

Answer 1

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:

1. Central subscribes to characteristic (either with notifications or indications)
2. Peripheral receives the subscribed callback so knows that the central is listening
3. Peripheral updates characteristic
4. Central receives characteristic updated notification

Central -> Peripheral:

1. Central writes characteristic
2. Peripheral receives write request update

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

• Performing common Central Role tasks
• Performing common Peripheral Role tasks

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.

Answer 2

If i understand you correctly you want the central to send data to your peripheral.

for that you use this method:

[peripheral writeValue:dataPacket forCharacteristic:writeChar type:CBCharacteristicWithResponse]

Answer 3

This is pretty compelling video to watch and know what exactly goes in iOS bluetooth framework. Its clearly explained what operations can be performed by central and peripheral systems.

https://developer.apple.com/videos/play/wwdc2012-705/