Player Controller and Viewport size in multiplayer gam

I know this must be easy thing to do, but still, how do I go if I want client player viewport size?
I’m making isometric shooter and I need it to get correct mouse cursor position, but everytime I try to get Player controller (which is, I suppose, holds viewport information) on client instance of the game I get nullptr.

APlayerController * PlayerController;

I’ve tried few ways:

Cast<APlayerController>(GetController());
PlayerController = Cast<APlayerController>(GetController()); 

And:

PlayerController = GetNetOwningPlayer()->GetPlayerController(GetWorld());

But both of them return nullptr on clients. Help pelase!

Did you find an answer? I’m asking the same thing over here, more or less: [Multiplayer BP] Viewport/Mouse Position Per Player Controller? - Programming & Scripting - Unreal Engine Forums