find publisher id when subscriber subscribe to topic in mqtt

Question

I am using mqtt in my nodejs backed application where there is communication with iot devices and where i am able to publish and subscribe to different topic.every thing is working well i can publish and subscribe to different topic.

I am able to send client id or the publisher id who publish topic in message part which is a repeated task for every publisher.

Is there any way we can know who is publisher while subscribing to topic. my mqtt client code at nodejs is

  var mqtt = require('mqtt')

  var url = "http://127.0.0.1:1883";

  var client = mqtt.connect(url);

client.on('connect', () => {
   console.log('Mqtt client connected to broker');
   client.subscribe('status/open');
   client.subscribe('status/close');
   client.subscribe('sendMsg');

})

client.on('message', (topic, message) => {
  console.log('new topic received at controller', topic);
  console.log('new messge received at controller', message.toString());
///is there any way to determine who is publishere here

 });

hardillb hardillb · Accepted Answer · 2018-01-05T13:05:16

No.

This goes against one of the core principals of pub/sub messaging, which is that a publisher shouldn't care who is subscribed to a given topic and a subscriber shouldn't care where the data is coming from, it just subscribes to a topic.

If you want to make it clear you have 2 options.

Use a topic structure that encodes the publisher in the topic and the subscriber uses wildcard topics to receive data from all publishers.
Encode the publisher information into the message payload.

find publisher id when subscriber subscribe to topic in mqtt

1 Answers