I am writing an MQTT subscriber in NodeJS using the mqtt package. The goal of this subscriber is to receive all messages coming to any/all topics but looks like the subscription to # (subscribe to all topics) does not seem to work. But when I replace # with an actual topic name it seems to work fine. Not sure why it is not working.
PS: the broker I am using is emqx.
Here is the code below.
const mqtt = require('mqtt'); const TOPIC = '#'; const HOST = process.env.HOST || 'localhost'; const PORT = process.env.PORT || 1883; const USERNAME = process.env.USERNAME || 'username'; const PASSWORD = process.env.PASSWORD || 'password'; const PROTOCOL = 'mqtt'; const clientOption = { port: PORT, host: HOST, username: USERNAME, password: PASSWORD, protocol: PROTOCOL }; const client = mqtt.connect(clientOption); console.log(`Connecting to mqtt://${HOST}:${PORT}@${USERNAME} topic:${TOPIC} ...`); client.on('connect', function () { console.log(`Connected!`); client.subscribe(TOPIC, function(err) { if(err) { console.error(err); } else { console.log(`Subscription to ${TOPIC} successful.`); } }); client.on('message', function (topic, message) { // message is Buffer console.log(`Incoming message to topic = ${topic} ...`); console.log(message.toString()); console.log('Preparing outbound message'); const outboundMsg = {...message, source: topic} console.log('Outbound message below'); console.log(outboundMsg); }); }); 1 Answer
Figured out the problem.
The issue was, I was running emqx inside a docker container, and emqx by-default blocks publishing and subscribing to $SYS/# and # topics.
This can be overridden in the etc/acl.conf file.
