MonoBehaviour.OnServerInitialized  

function OnServerInitialized() {
    Debug.Log("Server initialized and ready");
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void OnServerInitialized() {
        Debug.Log("Server initialized and ready");
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def OnServerInitialized():
        Debug.Log('Server initialized and ready')