AndFTP (your FTP client)

A nice light-weight app for doing exactly what I need it to do. It connects to my Synology SFTP server and mirrors the files to the SD Card. I was able to set up a one-way mirror in the free version. If sync is still limited to the pro version, that might mean two-way synchronizations. If you have file names with foreign characters be sure to change the character set in the advanced settings to UTF-8 (or whatever character set you need). Otherwise this app will silently change your filenames to fit within the specified character set. It does not warn you first. The scheduled synchronization feature will suffice. I would prefer an option to trigger synchronization when it gets plugged in for charging.

I use this app to communicate with my modded Nintendo Switch. I've been using FTP for a couple years on my PC to communicate with my Switch which is great and all, but when I just wanna extract a simple file like a video or something, it's annoying to whip out my laptop for that. Now I don't have to worry about that! It's just as fast as my PC but with the benefit of being right on my phone which is very convenient for something like a video I want to share. Great app!

It works, it's intuitive, and it supports batch transfers, but that's about all I can say for it. It sends a LOT of unnecessary commands to the server (CWD before every transfer I can maybe excuse, but LIST after every file while doing a batch upload? Really?) and it's appallingly slow. During large batch uploads, there are big gaps between files as if it's iterating O(n) over every file it's already sent. This can get up to multiple seconds with 100 files or so.