private void handleUpdate(UpdateResponse resp)
 {
     try
     {
         Console.WriteLine("Handling update");
         TicketSold ts = (TicketSold)resp;
         Console.WriteLine("New list of concerts : \n" + ts.Concerts);
         client.update(ts.Concerts);
     }
     catch (Exception e)
     {
         Console.WriteLine("Exception thrown in ProxyServer -- handle Update");
         Console.WriteLine(e.Message);
     }
 }