How do I ApplyDamage to a specific player across network

Assuming an RPC call is the correct way to do this...here is my pseudocode. The problem is that RPC "RemoteApplyDamage" is executed on all clients. I want it to execute just on the clients who are in attack range. Is there some ID I can use to identify the Player(s) to damage? I have tried using gameObject.GetInstanceID() but the local InstanceID of a game object seems to be different than the remote InstanceID of the same game object. I need to be able to handle both scenarios - enemies within the level (bots) and also enemies who are network players.

var AttackPowerJab:int;
var AttackPowerWhirl:int;
var AttackPowerCombo:int;

var attackPosition = new Vector3(0,0,0.8);
var attackRadius = 1.3;

private var attackJabHitTime = 1.0;
private var attackWhirlHitTime = 1.8;
private var attackComboHitTime = 1.8;

private var attackJabTime = 1.5;
private var attackWhirlTime = 2;
private var attackComboTime = 2;

private var waitHitTime = 0;
private var waitTime = 0;
private var attackPower = 0;

private var busy = false;

static private var InstanceID:int;

function Start(){

    InstanceID = transform.gameObject.GetInstanceID();

}

function Update(){

    if (Input.GetButton ("Jab")){
    	waitHitTime = attackJabHitTime;
    	waitTime = attackJabTime;
    	attackPower = AttackPowerJab;
    	if (!busy){
    		busy = true;
    		Attack();
    	}
    }
    else if (Input.GetButton ("Whirl")){
    	waitHitTime = attackWhirlHitTime;
    	waitTime = attackWhirlTime;
    	attackPower = AttackPowerWhirl;
    	if (!busy){
    		busy = true;
    		Attack();
    	}
    } 
    else if (Input.GetButton ("AttackCombo")){
    	waitHitTime = attackComboHitTime;
    	waitTime = attackComboTime;
    	attackPower = AttackPowerCombo;
    	if (!busy){
    		busy = true;
    		Attack();
    	}
    }

}

function Attack(){

    yield WaitForSeconds(waitHitTime);

    var pos = transform.TransformPoint(attackPosition);

    // enemies
    var enemies : GameObject[];
    enemies = GameObject.FindGameObjectsWithTag("Enemy"); 

    for (var go : GameObject in enemies) { 

    	var enemy = go.GetComponent(EnemyLifeMeter);
    	if (enemy == null)
    		continue;
    	Debug.Log("Distance: " + Vector3.Distance(enemy.transform.position, pos));
    	//Debug.Break();
    	if (Vector3.Distance(enemy.transform.position, pos) < attackRadius){
    		if (Input.GetButton ("Jab") || Input.GetButton ("Whirl") || Input.GetButton ("AttackCombo"))
    			enemy.SendMessage("ApplyDamage",attackPower);
    	}
    }

    // enemies that are network players
    var players : GameObject[];
    players = GameObject.FindGameObjectsWithTag("Player"); 

    for (var go : GameObject in players) { 

    	/* var player = go.GetComponent(PlayerLifeMeter);
    	if ((player == null))
    		continue;
    	*/

    	Debug.Log("Game Object: " + go.GetInstanceID());
    	Debug.Log("Me: " + InstanceID);
    	//Debug.Break();
    	if ((Vector3.Distance(go.transform.position, pos) < attackRadius) && !(go.GetInstanceID() == InstanceID)){
    		if (Input.GetButton ("Jab") || Input.GetButton ("Whirl") || Input.GetButton ("AttackCombo")){
    			//go.SendMessage("ApplyDamage",attackPower);
    			networkView.RPC ("RemoteApplyDamage", RPCMode.Others, attackPower, go.GetInstanceID());
    		}
    	}
    }

    yield WaitForSeconds(waitTime - waitHitTime);
    busy = false;

}

function OnDrawGizmosSelected(){

    Gizmos.color = Color.yellow;
    Gizmos.DrawWireSphere(transform.TransformPoint(attackPosition), attackRadius);

} 

@RPC
function RemoteApplyDamage (liferested:int, instID:int) {
    //playerObject = GameObject.FindWithTag("Player");
    //playerObject.SendMessageUpwards("ApplyDamage",liferested,SendMessageOptions.DontRequireReceiver);

    //var gos : GameObject[];
    //gos = GameObject.FindGameObjectsWithTag("Player"); 

    //for (var go : GameObject in gos) { 
    	//Debug.Log("InstID: " + instID);
    	//Debug.Log("go.InstID: " + go.GetInstanceID());
    	//Debug.Log("Name: " + go.name);
    	//if ((transform.gameObject.GetInstanceID() == instID)) {
    		//Debug.Log("-----------------Attacking: " + transform.gameObject.name);
    		SendMessageUpwards("ApplyDamage",liferested,SendMessageOptions.DontRequireReceiver);
    		//break;
    	//}

    //}

}

This isn't exactly an answer to your question (and let me know if I've missed something here), but if this is an MMO, you'd probably want to implement most of the player logic and damage calculation on the server, and simply pass the resulting values to all of the clients.

Even things like the (ifBusy) check need to be reproduced on the server, particularly to prevent client side hacks.

Someone else may have a better understanding of the Unity Multiplayer system, but fundamentally you may want to change the location of critical game logic first.

Seconding what Brian Kehrer says, you definitely would want to do the health managing server-side. I would, however, still transmit the RPC to all connected units - allowing clients to play hit effect animations when the character receives damage. Here's one example of how you could do it:

@RPC
function ReceiveDamage (damage : float)
{
	if (Network.isServer)
	{
		/*Apply the damage and figure out if the character dies - if
		so, the server should send a CharacterDied RPC to all*/
	}
	else
	{
		/*Play hit animation - maybe select between a
		few based on the damage value*/
	}
}

Hey Jamie, bit late but....

http://unity3d.com/support/documentation/ScriptReference/NetworkView.RPC.html

function RPC (name : string, target : NetworkPlayer, params args : object[]) : void

This can be done serverside or clientside, but having a list of players, players with the corresponding properties, and whenever applying damage/changing something just sending the corresponding id over an RPC is much easier:

//List of Network Players
var NPlayers:NPlayer[];

//Apply Damage
@RPC
function NPDamage(id:int, amount:float) {
    for (obj in NPlayers) {
        if (obj.id == id) {
            obj.health -= amount;
            //Other things like effects and such
            break;
        }
    }
}

This is the method I always use, as it works quite well, even in a client based game.

how do I determine which player to subtract the hit points from though?