On Android 5.0 & higher, to access external SD card, in app settings, click mount folder, select "custom" and then select the external SD card in the next screen.
https://www.youtube.com/watch?v=Xaqc11qq-Uw
Convert your android phone/tablet into a FTP Server! Use this free app to host your own FTP Server on your phone/tablet. Use the FTP Server to transfer files, photos, movies, songs etc...to/from your android device using a FTP client like FileZilla.
Key features:
- Complete FTP server with configurable port number
- Supports FTP over TLS/SSL (FTPS)
- Configurable anonymous access
- Configurable home folder (mount point)
- Configurable user-name/password
- Avoid using USB cables for file transfer and copy/backup files over Wifi
- Works over Wifi and Wifi tethering mode (hotspot mode)
Steps to use the app:
- Connect to WiFi network and open app.
- Click the start button
- Key in the server URL in a FTP client or windows explorer and transfer files