How are you trying to download the image from your Edison? I'd suggest you to use the SFTP protocol since, to me it's the easiest way to transfer files. I did a quick test with the free app Turbo FTP client & SFTP client, and I had no issues with it. I know you probably needed your own app for other reasons but you can check that app to see how it works and maybe take inspiration from it.
Let us know,
Do you have updates on this? Have you tried with the SFTP protocol?
No I didn't get the solution. The same problem is going on.
but as of now, I have installed apache server to download files contained on my edison.
Please update me if you get any solution.
In Wi-Fi Direct data transfer between two Intel® Edison devices through FTP, you can see how to implement the SFTP document through a Wi-Fi direct connection using the openssh-sftp package, why don't you check it, it might help be of help for your project.
I'll surely implement it and let you know about the progress..