Using OnMouseDown to send RPC, along with ID of clicking player

I'm brand new to networking, and I'm making a 2 player card game.

I've got a deck of cards with a collider on it, which I'm using to detect OnMouseDowns. In there, I call the Deal() function (an RPC), which deals all the cards to both players. My issue is that I only want one player to be able to deal, so if the non-dealer clicks on the deck, nothing should happen. How can I send the ID of the player who clicked on the deck to the RPC Deal() call, so that the server can check if they are the current dealer?