Cheating possible in this code?

Hello there! I just started with Networking , and I am using RPC calls at the moment (I use Photon ). Here is a little code, that , makes me curious if it can be cheated by players.

What it does, is ,the player sends an rpc to the server, then the server responds to the players for a limited time ( the rpc can be called only 4 times ). Can this be cheated?

 using UnityEngine;
 using System.Collections;
 
 public class TestThing : Photon.MonoBehaviour {
 
     //by player
     float localvar = 12;
     //by server
     int server_times = 4;
     float server_var;
 
     // Update is called once per frame
     void Update () 
     {
         //we call the server only!
         if( Input.GetKeyDown(KeyCode.L) )
         {
             //request from server
             photonView.RPC( "ToServer",PhotonTargets.MasterClient );
         }
     
     }
 
     //this is what player requested
     //called on server only
     [RPC]
     void ToServer()
     {
         if( server_times >0 )
         {
             photonView.RPC( "ToPlayer" , PhotonTargets.Others , (object)20f );
             server_times -= 1;
         }
     }
     
     //called back on player ,after the player has requested it
     [RPC]
     void ToPlayer( float thevar )
     {
         localvar += thevar;
         print(server_times);
     }
 
 }