One app to serve them all
This app can start a http-server from an android/ios device binding to the port specified by the user (default 8888) and expose a directory from the device specified by the user (default dir /sdcard/Downloads).
Any device connected to the same wifi network and with a web browser, can navigate to the server url or scan the QR code to access the directory exposed
Currently there is no authentication from the app end. The app assumes devices connected to the same wifi network as the user is already authenticated. Do not use the app in a public wifi.