private async void btnSendCloudMessage_Click(object sender, EventArgs e)
        {
            var pImei = txtIMEI.Value;
            if (String.IsNullOrEmpty(pImei)) pImei = "352961067289634";
            
            var args = new { func = 17, imei = pImei, messages = txtSentMessage.Value, userid = 100 };
            var result = await CustomClient.Instance.InvokeAsync<string>("ApiPostAsync", Properties.Settings.Default.CloudMessagingUrl, args.SplitProperties());

            // respons sample: {"text":"true","err":"ir.shoniz.NO_ERRORS_MESSAGE"}

            MessageBox.Show(result);
        }