Connect this phone to the C440

Follow the steps in order. About two minutes, once, then it's permanent.

1 Install Tailscale

Open the Play Store on this phone and install Tailscale.

Open in Play Store Tailscale install QR

Scanning the QR also opens the Play Store page.

2 Sign in

Easiest: tap Sign in with Google and pick the account that owns the network.

Or tap Use an auth key and scan the key QR shown on the C440 screen.

Look at the C440 screen. The key QR is displayed there — scan it with your phone camera, copy the text it gives you, and paste it into the app. It works once, then it's dead.

The key never lives on this page, because this page is public. The C440 screen is not.

3 Start the file bridge

Install Primitive FTPd, then set it up:

Open in Play Store F-Droid

Anonymous login: ON (no username, no password)
IP to bind to: your phone's Tailscale IP (the 100.x.x.x from the notification once Tailscale is on)
Start the server. Keep the default port.

4 Connect

Once Tailscale says Connected and the file bridge is running, tap below. This pings the C440, which will then open this phone's files on its screen.

Connect to the C440

5 Finished

The C440 sees this phone the moment it joins. The folder gets bookmarked on the C440 side automatically — from now on it's one click in the file manager to view and manage everything on this phone.