Autodiscovery not working on iOS 1.3.1 (15) | Swiftfin is missing `com.apple.developer.networking.multicast`

[kunzese]

Describe the bug

I just installed Swiftfin on my iPhone and noticed that the autodiscovery of local servers is not working. The Connect (Verbinden) screen just tells me that there are no local servers (Keine lokalen Server gefunden).

Using 'tcpdump -i any -s0 -A udp port 7359" on the server I was able to confirm that no udp pakets arrive on port 7359.

Local network permission has been granted to the app.

On my AppleTV the autodiscovery in the Swiftfin app works though.

Application version

1.3.1 (15)

Where did you install the app from?

App Store

Device information

iPhone 16

OS version

iOS 18.5 (22F76)

Jellyfin server version

10.10.7

[samglt]

In ServerDiscovery I see that the broadcast is failing with the error "UDP connection failed to send data: No route to host" which is mentioned in this issue in the UDPBroadcastConnection package we're using as being possibly related to needing the multicast networking entitlement, which is needed even when debugging on a physical device.

There may be another problem here as well though, because multicast works in the simulator but I can't discover my server there either.

[JPKribs]

needing the multicast networking entitlement

That sounds right IMO.

I have a branch on the SDK to rework Server Discovery: jellyfin/jellyfin-sdk-swift#47

This is a bit more robust and works in a standalone app but we appear to have the same issue using this one. Which makes me believe we're missing something.

On a somewhat related note, I am also unable to find servers on other iOS apps too. StreamyFin & Infuse both appear to have this issue as well for me. So could be device/network related.

[samglt]

Doing a bit more testing, if I use the simple receive_and_reply.py server in UDPBroadcastConnection to manually reply with the discovery payload, Swiftfin will receive it and handle it properly (in the simulator). That means nothing's wrong with the app beyond needing the entitlement, and I just don't have my networking set up right.

[JPKribs]

But, why does this work from the simulator? I guess that's my confusion the simulator works fine for me for 1.3 / 1.4 / Main but none of those work on real hardware.

[samglt]

Because Apple's decided to limit it this way for some reason. From an official article about multicast:

Note: You can test your app using the iOS and iPadOS simulators without an active entitlement, but using multicast and broadcast networking on physical hardware requires the entitlement.

[JPKribs]

Because Apple's decided to limit it this way for some reason. From an official article about multicast:

Apologies, I thought your previous message was suggesting this wasn't multicast. I'll lean on @LePips but I believe we are approved for multicast. That being said, I'm unsure if there are additional steps required from that point.

[samglt]

I'm not totally sure what I'm talking about either, but that article talks about broadcast and multicast as both needing this entitlement.

I didn't know we already had Apple's approval, I think that means all we have to do is add com.apple.developer.networking.multicast to the Swiftfin.entitlements file and then discovery will work in the next App Store release. The only annoyance I've encountered with that is that XCode won't build unless you personally have that entitlement approved for the bundle ID in your own developer account, so for first-time contributers to build and test Swiftfin they'll have to remove that line in the entitlements file.

[samglt]

I got my personal entitlement approved and now I can get my own builds on physical hardware to send broadcasts, so it is just a matter of adding the above entitlement to the Swiftfin.entitlements file.