Which method allows a Unity game to call a server-side function from the client?

The method that allows a Unity game to call a server-side function from the client is the [Command] attribute. In Unity's networking framework, particularly in the context of UNet or other similar networking solutions, the [Command] attribute is used to indicate that a method should be executed on the server when called from a client.

When a client invokes a method marked with [Command], it sends a request to the server to perform that function, allowing the server to execute logic that may affect the game state or manage authoritative aspects of gameplay. This is crucial in networked games where clients may interact with a shared game state, ensuring that critical operations remain controlled on the server to maintain integrity and prevent cheating.

The other methods listed do not serve this specific purpose within the Unity networking paradigm. For instance, while terms like RpcCall, InvokeServer, or SendToServer may seem plausible, they do not correspond to the standard approaches provided by Unity for executing server-side functions from client calls. Understanding the role and usage of commands is essential for managing networked interactions in multiplayer games effectively.