Summary: Looking for software to transfer files between 2 Android phones over WiFi.
Ease of setup.
If I want complicated, I can just run FTP servers on them and use FTP clients.
Ideally, all the setup I want is to either enter the IP of another phone, or better yet list devices on local WiFi network and let me pick one. Even better if it autofilters for devices with identical software installed.
Ability to transfer an entire directory (not required to sync... just assume fresh directory NOT present on transfer phone)
VERY lightweight when not in use.
- Either ability to permanently exit with no background service; OR background service that's extremely low memory footprint - under 1 MB - and no resource usage when idle.
Ability to read/write any files on filesystem, more specifically, on external SD card.
No reliance on cloud storage or ANY infrastructure aside from these 2 phones
Compatible with Android 4.3 and 4.4
Retry capability if transfer gets interruted
Optional desired features
Ability to remember what the last phone you connected to was; or which directories were used last.
Cost: preferably gratis. But I don't require that.
Reasonable speed (e.g. shouldn't be any more than 2x slower than FTP). But I'm willing to tolerate slower transfer speed for higher quality features
ability to operate from a single phone. E.g. I'm fine if I have to pick a source directory on source phone but a target directory on target phone
Ability to transfer over non-WiFi.