How to send a gameobject in the OnSerializeNetworkView()

Hello, I'm a beginner with network. i have a multiplayer scene. each player can have a "Target", the target is another gameobject (another player, or a environment élément).

But, when i want to send the player script parameters on the network with OnSerializeNetworkView, i cannot send his target.

per exemple : If I send a integer "health" , it work fine

 > public int currentHealth; void
 > OnSerializeNetworkView(BitStream
 > stream, NetworkMessageInfo info) {
 >     int health = 0;
 >     if (stream.isWriting)
 >     {
 >         health = currentHealth;
 >         stream.Serialize(ref health);
 >     }
 >     else
 >     {
 >         stream.Serialize(ref health);
 >         currentHealth = health;
 >     } }

But when i send a transform, or gameobject, it dont work

 public Transform currentTarget;
 
 void OnSerializeNetworkView(BitStream stream, NetworkMessageInfo info)
 {
     Transform target ;
     if (stream.isWriting)
     {
         target = currentTarget;
         stream.Serialize(ref target);
     }
     else
     {
         stream.Serialize(ref target);
         currentTarget = target;
     }
 }

http://docs.unity3d.com/Documentation/ScriptReference/BitStream.Serialize.html i read tere, i can only use bool, char, short, int, float, Quaternion, Vector3 and NetworkPlayer

So, how can i send my player target, if i cannot send Gameobject, of transform.. ? I tried to send the gameobject ID, but i canot getting the gameobject back with it.