I know the FIND protocol is used to discover which LRUs are available if the data loader supports the FIND protocol. I also know the message is sent as a broadcast using UDP, but what is in the message that's being broadcasted?
Attachment 3 of ARINC 615A-3 describes the FIND function. The FIND protocol has an Information Request (IRQ) packet and an Information Answer (IAN) packet. Each packet contains a 2 byte header and a variable length data portion.
3-4 Information Request Packet
Source MAC address should be the MAC address of the data loader (or the initiator.
Destination MAC address should be a unicast, multicast, or the broadcast MAC address.
Source IP Address should be the IP address of the Data loader (or the initiator).
Destination IP address should be a unicast, multicast, or a broadcast IP address (full broadcast i.e., 255.255.255.255 or class-relevant broadcast e.g., 188.8.131.52 for a class C).
Opcode value should be IRQ (0x0001).
Data list should be a null ASCII string with terminator: 0x00.
Packet is terminated by 0x10.