File upload/download with resume transfers?

Hi everyone.

Can you guys share your opinions on what the best way to do a desktop app that does file uploads/downloads to/from a web site with file transfer resuming?

If I’m uploading a file and the connection is broken what’s the best xojo way to later continue the file transfer without having to start all over again?

I’d like to hear different opinions of various ways :

Http socket with a php script?

FTP using the shell?
CURL using the shell?

Are there any free or reasonably priced plugins of doing file transfers to a website that have resume function already built in?

Thank you.