As an alternative, would it be possible to send the LAN Sync broadcast to the subnet's .255 style IP address, e.g., 192.168.1.255?
Seems like some routers cannot handle certain broadcast scenarios.
As an example, on my Verizon FiOS Quantum Gateway router, if I manually send a UDP packet to 239.192.0.0, no other client receives the packet. However, if I do the same to 192.168.1.255, then all devices receive the packet.
Test bed is using 'socat' program to generate UDP packets.
WORKS
socat - UDP-DATAGRAM:192.168.1.255:3838,broadcast
DOES NOT WORK
socat - UDP-DATAGRAM:239.192.0.0:3838,broadcast