What is the beacon DFU How can I use it?

[GunMin]

First, I flash the softdevice, then I flash the bootloader, then I use a smartphone app to upload an application to the device via BLE.

but, The first operation only. When I try to re-download, Is not a search.

How do I use it?

and if I sell it by creating a product, creating Does any way?

Did I put a hex file for the application in any way with the product? (How to load the application when I create a product)

[GunMin]

1. I flash the Softdevice and Bootloader using nRFgo Studio. and Download the application using Keil uVision4.

2. I flash the Softdevice and Bootloader using nRFgo Studio. then I use a smartphone app to upload an application to the device via DFU.

Case 1 is no operation. and Case 2 is operation. but if I re-upload application to the device via DFU, No operation.