private async Task AddHub(string address)
{
    Trace.TraceInformation("AddHub: " + address);
    // create a connection to a hub
    var hubConnection = new HubConnection(address);
    hubConnection.Headers.Add("ORLEANS", "GRAIN");
    var hub = hubConnection.CreateHubProxy("playerHub");            
    await hubConnection.Start();
    hubs.Add(address, new Tuple<HubConnection, IHubProxy>(hubConnection, hub));
}