Android <-> Linux on local network simply does not connect

I’m running the latest Syncthing version 1.16.1 installed from the repository on Linux Mint 20.1, and I want to sync folders with my rooted OnePlus 3 running Android 10 only while both devices are connected to my home wifi.

I’ve added each device to the other one with the ID, specified the folders to be synced and shared, but…nothing. It refuses to connect. I’ve also turned off NAT traversal, global discovery and relaying since I only want to sync when both devices are on the local wifi network.

Folders appearing as ‘up to date’ also makes no sense - up to date compared to what, given they have never been synced? Is there a way to force a scan of the local network?

When I view the log on my laptop, it just says

Device <my phone's ID> is "" at [dynamic]

On my phone, the laptop shows up as ‘disconnected’, and each devices reports the last seen of the other as ‘never’. No firewall on either device.

They are up to date to the latest global state, which if they never connected, is effectively their own.

As usual, for local network stuff, I’d verify that you don’t have AP isolation, the devices are on the same subnet and that you can ping the other device.

If that works, then its most likely a firewall or the router not allowing multicast packets.

You can always hardcode device addresses.

Also, as of recent versions, global discovery helps with local connectivity, as we announce local addresses, so even if multicasts don’t work, they should be able to find each other local addresses via global discovery.

You can always hardcode device addresses.

Thanks, that seemed to do the trick. I also enabled global discovery - do I need it on if I’m specifying the address? I’ve set up static DHCP on my router to ensure both devices always get the same addresses.

If you hardcoded addresses, then probably not.

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Btw the Android might need a multicast permission granted to the app, depending on manufacturer specific handling of multicast (local discovery) messages in its firmware. Applies primarily to Android 11, but I’ve read somewhere 10 devices may also be affected.

How does one grant that?

Sorry , you cannot do it yourself. The app needs “the code” to do it.

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