Android : "FAILED BINDER TRANSACTION" when using SignalR client

I'm developing an app that uses this library from Microsoft SignalR team, it seems great. Now I wanna use it in my android application, so I'm using it this way:

HubConnection connection = new HubConnection(DEFAULT_SERVER_URL);
final HubProxy proxy = connection.createHubProxy("FitnessHub");
connection.error(new ErrorCallback() {
        @Override
        public void onError(Throwable error) {
        }
});
connection.start().done(new Action<Void>() {
        @Override
        public void run(Void obj) throws Exception {
            proxy.invoke("showNotification", new Object()).done(new Action<Void>() {
                @Override
                public void run(Void obj) throws Exception {
                    Toast.makeText(getApplicationContext(), "Hello", Toast.LENGTH_LONG).show();
                }
            });
        }
    });

Hub:

public class FitnessHub : Hub
    {
        public void SendNotification()
        {
            Clients.Others.showNotification();
        }

    }

But, I always getting this error in LogCat:

!!! FAILED BINDER TRANSACTION !!!

channel 'b13f7160 com.example.signalrclient/com.example.signalrclient.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!

Any idea?