OPC-DA Disconnect issue|Classic OPC: DA, A&E, HDA, XML-DA, etc.|Forum|OPC Foundation

When I connect to the Opc server (opc-da), a new client is created. But when I close the connection, the client number does not change. When I connect again, a new client is created.

Each new connection creates a new client. The number of clients is increasing because I can not close the clients.

How can I reduce the client when I close the connection?

Used dll:  OpcNetApi.dll, Version: 1.30.3.0

public void StopConnection()
{
      GroupRead.DataChanged -= DataChanged;
      GroupRead.Dispose();
      Server.Disconnect();
      Server.Dispose();
}

public Opc.Da.Server Server { get; set; }
public Opc.Da.Subscription GroupRead { get; set; }

public Result StartListening()
{
    Result result = new Result(true);

    try
    {
        var surl = string.Format("opcda://{0}", MyOpcClientClass.ServerName);
        var url = new Opc.URL(surl);
        Server = new Opc.Da.Server(new OpcCom.Factory(), null);
        Server.Connect(url, new Opc.ConnectData(new System.Net.NetworkCredential()));

        Server.ServerShutdown += ServerShutdown;

        var group = new Opc.Da.SubscriptionState();
        group.Name = MyOpcClientClass.GroupName;
        group.UpdateRate = MyOpcClientClass.Period;
        group.Active = true;

        GroupRead = (Opc.Da.Subscription)Server.CreateSubscription(group);
        GroupRead.DataChanged += new Opc.Da.DataChangedEventHandler(DataChanged);

        var items = this.MyOpcClientClassFieldMappingList.Select(i => new Opc.Da.Item
        {
            ItemName = i.OpcTagName
        }).ToList();

        GroupRead.AddItems(items.ToArray());

    }
    catch (Exception e)
    {
        // error log
    }

    return result;
}

private void DataChanged(object subscriptionHandle, object requestHandle, Opc.Da.ItemValueResult[] values)
{
    try
    {
        // do smth...
    }
    catch (Exception e)
    {
        // error log
    }
}