Unique ID for LAN

Hi there!
Im saving game sessions using save/load game system in server and link the right saved game when client joins the same server and using the Unique Steam ID.
I wonder how can I do the same in LAN games. How can I get a Unique ID but for LAN.
Maybe using IP?
Using MAC Address?

And how can I get it?
How would you solve this?

Thank you.

Maybe GetDeviceID
but if player change computer/device it will be different

Thnx! Ill try getdeviceid.
Do you know how it get that number?
Which info this node takes to define that reference?