How do you identified RPC sender without any networkID?

Another quick question, I’m used to having this unique networking ID attach to any of my RPC calls. But I don’t see any of that in UT4 c++ networking.
There’s FUniqueNetId but it’s a TSharePtr, and I don’t really get how I can use this with RPC calls. There’s local player ID, but it’s always 0 across clients.

So… I’m confused. How do you identify who sends what to the server?

update I’m sending PlayerId from PlayerState. This seems to work fine.