bool _loginToCamera(string ip, string user, string pass, ref Dut.IPCamera <U> camera)
        {
            bool ret   = false;
            int  count = 0;

RE:
            count++;
            camera = new Dut.IPCamera <U>(uploadInfo, ip, user, pass);
            camera.Login();
            ret = camera.IsConnected();
            if (!ret)
            {
                if (count < 3)
                {
                    goto RE;
                }
            }
            return(ret);
        }