Transmit collection of information to mqtt using Node.js

Question

Transmit collection of information to mqtt using Node.js

I'm facing an issue with sending an array of data from my node to the MQTT server.

Although I have a receive function that is working fine, I'm unable to get it working in the opposite direction.

  var message = new Array();
  message[0]  = 108;
  message[1]  = 11;
  client.publish("/topic", message, {
            retain: false,
            qos: 0
        });

However, I keep receiving the following error:

[ERROR] TypeError: invalid data

I'm unsure of how to properly declare the array in order to populate it with data and send it. In my receive function, the message variable is passed as an argument and I can access it as an array: message[x]...

javascript arrays mqtt

Answer 1

Answer №1

When working with mqtt, you have the option to use Buffer or String data types.

If you need to use typed arrays, you will first need to convert them to buffers. You can achieve this by using the npm module available at https://www.npmjs.com/package/typedarray-to-buffer.

var toBuffer = require('typedarray-to-buffer')
  var message = [];
  message[0]  = 108;
  message[1]  = 11;
var arr = new Uint8Array(message)
arr = toBuffer(arr)

/*
arr.toString()  // '\u0001\u0002\u0003' 
arr.readUInt16BE(0)  // 258 
*/
// The array has been successfully converted to a buffer! 
  client.publish("/topic", arr, {
            retain: false,
            qos: 0
        }, function(){
  console.log("message published"));

Answer 2

When working with mqtt, you have the option to use Buffer or String data types.

If you need to use typed arrays, you will first need to convert them to buffers. You can achieve this by using the npm module available at https://www.npmjs.com/package/typedarray-to-buffer.

var toBuffer = require('typedarray-to-buffer')
  var message = [];
  message[0]  = 108;
  message[1]  = 11;
var arr = new Uint8Array(message)
arr = toBuffer(arr)

/*
arr.toString()  // '\u0001\u0002\u0003' 
arr.readUInt16BE(0)  // 258 
*/
// The array has been successfully converted to a buffer! 
  client.publish("/topic", arr, {
            retain: false,
            qos: 0
        }, function(){
  console.log("message published"));

Transmit collection of information to mqtt using Node.js

Answer №1

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