I don't know; it's automatic and just works. My program just dumps the image and text files to its local folder and doesn't know that Dropbox is running. Similarly, it looks to see if a command file exists in the folder; if so, it executes and deletes it. I can also run Windows command files, or update the programs, or reboot the remote PC. Sort of a hobby project.
A previous generation of this system used an FTP server, not Dropbox; that was a nightmare. The current version has been absolutely reliable. Dropbox handles the networking.
My PowerBasic program in the cabin writes the files to the local folder about once a minute, and Dropbox might take a few seconds to dissiminate the files to the world.
Dropbox makes this sort of distributed system trivial. Just write a file to a local folder, and it's replicated on other computers without any network concerns.