Hi All,
FTP requires two TCP/IP channels, one that stays connected the whole time for comands and a separate one for the data transfer that can go up and down throughout the process of moving data.
I think this is very much possible on the Spark core, but memory could be challenge. I have been thinking about a FTP server rather than a client for the core, but the work is about the same really. There is a somewhat incomplete Arduino library for an FTP server that could be a starting point.
One question is, how much data to you have to transfer and how quickly or slowly do you need it?
You could do a simple transfer using Spark.function() and Spark.publish() as long as you didn’t exceed the publish rate limit of one per second on average. That would get you somewhere around 64-bytes per second but would be very easy to implement today.