MasterServer HostList is always empty

Hey, I ve got a problem. The Masterserverhostlist is always length 0. Dont know what I did wrong. Hope somebody can help me out. This is my NetworkBase Class methods which are important:

    void Update()
	{
		if(_hostData.Length != 0)
			_hostData = MasterServer.PollHostList();
	}
	
	
	/// <summary>
	/// Starts the server.
	/// </summary>
	/// <param name='pPlayer'>
	/// P player.
	/// </param>
	public void StartServer(int pPlayer)
	{
		bool useNat = !Network.HavePublicAddress();
		Network.InitializeServer(pPlayer,NetworkData.GamePort,useNat);
	}
	
	/// <summary>
	/// Registers the host.
	/// </summary>
	/// <param name='gameName'>
	/// Game name.
	/// </param>
	public void RegisterHost(string pGame)
	{
		MasterServer.RegisterHost(NetworkData.GameName,pGame);	
		Debug.Log("Host registered");
	}
	
	/// <summary>
	/// Requests the hosts.
	/// </summary>
	public void RequestHosts()
	{
		MasterServer.ClearHostList();
		MasterServer.RequestHostList(NetworkData.GameName);
		Debug.Log ("Send Host request");
	}

After calling StartServer and RegisterHost the length of _hostData is still 0. What did I wrong?

These two lines make not much sense:

if(_hostData.Length != 0)
    _hostData = MasterServer.PollHostList();

The list will be empty at the beginning and you only poll the list when it’s not empty… It can never get filled because PollHostList is the function that should fill the array, but you don’t call it—