How do you send the data to hex in MQTT?

MIT App Inventor Help
1

I have an MQTT gateway for Modbus that needs to receive in hexadecimal. How can I do this?

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2

No-one seems to have an answer for this. Have you made any progress ?

3

Maybe you could encode it to base64 and then decode it at other end. I have done it in my tutorial, I encoded and decoded the image to base64 and sent it through MQTT.

4 
<!DOCTYPE html>
<html>
<head>
     <title>
         How to convert image into base64 string using JavaScript ?
     </title>
</head>

<body>
     <input type = "file" name = "" id = "fileId" onchange = "imageUploaded()" >
     <br><br>
     <button onclick = "displayString()" >
         Display String
     </button>

     <script>
         let base64String = "";

         function imageUploaded() {
             let file = document.querySelector(
                 'input[type=file]')['files'][0];
             let reader = new FileReader();
             console.log("next");
             reader.onload = function () {
                 base64String = reader.result.replace("data:", "")
                     .replace(/^.+,/, "");
                 imageBase64Stringsep = base64String;
                 // alert(imageBase64Stringsep);
                 console.log(base64String);
             }
             reader.readAsDataURL(file);
         }

         function displayString() {
             console.log("Base64String about to be printed");
             alert(base64String);
         }
     </script>
</body>

</html>
5

Please do you have a video that explain How can I send and receive data from MQTT machine to my app inventor?