How to Send data as JSON objects over to MQTT broker

Question

I'm using eclipse paho client on ubuntu and trying to send latitude, longitude and timestamp information as JSON format to the MQTT broker. How do I do that?

I found this article, But its not complete.

Thyratron

Answer 1

You just need to create your JSON object as a string then call getBytes() on that string to get the byte array to use as your payload in the message.

 MqttMessage message = new MqttMessage();
 message.setPayload("{foo: bar, lat: 0.23443, long: 12.3453245}".getBytes());
 client.publish("foo", message);

Osbourne

You better use String.getBytes(StandardCharsets.UTF_8) because if you not specify the charset it will use your platform defaults which may not UTF-8 (JSON is normally UTF-8) – Fissiparous

Answer 2

I don't know about that, but I use his:

#!/usr/bin/python
import json
import paho.mqtt.client as mqtt


send_msg = {
        'data_to_send': variable1,
        'also_send_this': variable2
}

client.publish("topic", payload=json.dumps(send_msg), qos=2, retain=False)

Koziarz

Answer 3

If you're using JavaScript, than you can use:

client.publish("foo", JSON.stringify({"foo": bar, "baz": 123})) // on sender side, and

JSON.parse on the receiver end.

Wastebasket