On server there is no first person camera. Unless it is listen server then you have camera but only for PlayerCharacter that hosts game.
I solved this different way:
- i calculate beginning and end of trace in local, client player character.
- then i do remote procedure call (ie event that runs on server), give it beginning and end then escalate to server.
- then server side i do all traces.
You also should make check if you run really client code or mixed client server code when you have listen server.
If you want to make dedicated server, go for mixed listen server, but instead of default player controller and player pawn on listen server spawn some kind of spectator that lets you see what is going on. There are some amusing things in unreal when dealing with client, server and “listen server client”. You need to sort it all out (and understand) else it will confuse you forever.
ps. that whole thing of mixing code for client and server in same blueprint is very confusing.