Ntfy on Android: can't connect to Ntfy server (on wifi) behind VPN when restricted to wifi only

[GideonBear]

🐞 Describe the bug

When I set Ntfy to "wifi only" in my settings (Samsung), it fails to connect to my Ntfy server over a WireGuard VPN, even on wifi (mobile data is off). When "Mobile data or wifi" is selected, it connects fine.

💻 Components impacted

Android app

💡 Screenshots and/or logs

https://nopaste.net/9iBLnfgCnN

🔮 Additional context

When "wifi only" is selected, I do get notifications over mobile data. Attachments fail to download.
This is probably related, and also an issue for me; I want to use as little mobile data as possible.

[Ravindranathrl]

I've investigated this issue and found that it likely stems from how the WireGuard VPN routes traffic when restricted to "Wi-Fi only." The error logs indicate a java.net.ConnectException: Failed to connect to /172.17.0.1:1420, which suggests that the app is trying to connect to a local IP that may not be accessible over the VPN when only Wi-Fi is enabled.

Add the following to your WireGuard configuration to ensure all traffic, including Wi-Fi-only traffic, routes through the VPN:

AllowedIPs = 0.0.0.0/0, ::/0
PersistentKeepalive = 25

Use a Public IP Address Instead of a Local IP:

Replace 172.17.0.1 with the public IP address or domain of your Ntfy server. This ensures that traffic is routed correctly through the VPN tunnel, even on Wi-Fi.

Adjust Android VPN Settings:

Set the VPN to Always-on VPN and enable Block connections without VPN in Android settings.

Disable Mobile Data Always Active in Developer Options (if available) to force the device to rely entirely on Wi-Fi.

Check App Permissions:

Ensure that the app has these permissions in the Android manifest: