Sprocket and Bluetooth iOS protocol for custom app

[TristanPct]

I'm currently developing an iOS app to directly connect to my HP sprocket printer but I'm stuck with the bluetooth data I have to send to the printer.

My phone and my app correctly pair with the printer but when I send the encoded jpeg file to the printer nothing happens (no printing, no error code from bluetooth return)...

I encode my image with:

let imageData = UIImageJPEGRepresentation(myUIImage, 1.0)

And send the file using iOS ExternalAccessory framework:

imageData.withUnsafeBytes { outputStream.write($0, maxLength: imageData.count) }

Do I have to send a specific code before or with image data?

Has anyone developed a custom app for this printer (or a similar one)?

I have read that a Windows computer connected with bluetooth to the sprocket can print just by sending jpeg or png files, I try to reproduce that with my iOS app.