We are using UDP messages in an exposition to synchronise audio on mobile devices with video shown in the exposition. (I know that this might not be the best choice, but it wasn't ours.)
This works perfectly for the devices (based on Android) that can be boroughed there. And it worked on my personal Android and iOS devices when I tested it there last year, too. As some problems with the sync were reported, I tested the set up in my local network again:
Raspberry broadcasting UDP messages (to 255.255.255.255)
I can receive those messages on my local linux machine, on one of my Androids (with Android 13), and on my iOS, without problems.
But the device with Android 12 (which worked before -- I am sure, as this is the device I tested with in the exposition), is not receiving the broadcasted messages. I tested with the same Apps as on the other.
Changing the broadcast to just one IP address (the address of the Android 12), it works, the device is receiving the messages.
I used following Apps to test:
- "Tcp Udp Server & Client" and "UDP-TCP-REST Network Utility" on Android
- "TCP/UDP Server/Client" on iOS
tcpdumpandncon my linux machine
I read about MulticastLock. And I do not know if the Apps I used for testing use this or not. But if not, why is one Android receiving messages and the other is not?
Are there any settings affecting this behaviour?