Question: AWS IoT Core / mqtt.js - After Successful Topic Subscription, Still Not Able To Run a Callback On a Message

[adrians5j]

I'm trying to use the mqtt.js library in order to interact with the AWS IoT Core endpoint with the following code:

const mqtt = require("mqtt");

const IOT_ENDPOINT = "wss://xxxxxx-ats.iot.eu-central-1.amazonaws.com";
const client = mqtt.connect(`${IOT_ENDPOINT}/mqtt?x-amz-customauthorizer-name=Authorizer`);

client.on("connect", () => {
    client.subscribe("xyz", err => {
        if (!err) {
            // Works, I can see the message in AWS Console / MQTT test client.
            const dt = new Date().toISOString();
            client.publish("xyz", JSON.stringify({ message: "CURRENT DT:" + dt }));
        }
    });
});

// The callback never gets executed, nothing is printed in the console.
client.on("message", (topic, message) => {
    console.log("Message received.");
    client.end();
});

What's interesting is that I can see the published message in the xyz topic in the AWS Console / MQTT test client. Great!

What I can also see is that there are no messages being printed in my terminal, despite the fact that the client.subscribe call did not throw any errors (in other words, topic subscription was successful), and I am able to publish messages on the same topic from the AWS Console / MQTT test client.

I've tried multiple things, changing params when connecting, trying different variations of the code, no luck 😩.

My next idea on how to debug is to try enabling IOT CW logs and see if anything is logged in there maybe.

Until then, my question is: anybody have any suggestions on what else to check why nothing is being printed in my terminal?

Thank you!🍻

[robertsLando]

@adrians5j Are you running it on nodejs or browser? If nodejs you can add the env var DEBUG=mqttjs* in order to see more logs on your side, if you want try to upload them here and I will give them a look

[adrians5j]

DEBUG=mqttjs* node mqtt.js 
  mqttjs connecting to an MQTT broker... +0ms
  mqttjs:client MqttClient :: version: undefined +0ms
  mqttjs:client MqttClient :: environment node +0ms
  mqttjs:client MqttClient :: options.protocol wss +1ms
  mqttjs:client MqttClient :: options.protocolVersion 4 +0ms
  mqttjs:client MqttClient :: options.username undefined +0ms
  mqttjs:client MqttClient :: options.keepalive 60 +0ms
  mqttjs:client MqttClient :: options.reconnectPeriod 1000 +0ms
  mqttjs:client MqttClient :: options.rejectUnauthorized undefined +0ms
  mqttjs:client MqttClient :: options.properties.topicAliasMaximum undefined +0ms
  mqttjs:client MqttClient :: clientId mqttjs_c8471ff3 +0ms
  mqttjs:client MqttClient :: setting up stream +0ms
  mqttjs:client connect :: calling method to clear reconnect +0ms
  mqttjs:client _clearReconnect : clearing reconnect timer +0ms
  mqttjs:client connect :: using streamBuilder provided to client to create stream +0ms
  mqttjs calling streambuilder for wss +2ms
  mqttjs:ws streamBuilder +0ms
  mqttjs:ws createWebSocket +1ms
  mqttjs:ws protocol: MQTT 4 +0ms
  mqttjs:ws creating new Websocket for url: wss://xxxxxx-ats.iot.eu-central-1.amazonaws.com:443/mqtt?x-amz-customauthorizer-name=Authorizer and protocol: mqtt +0ms
  mqttjs:client connect :: pipe stream to writable stream +20ms
  mqttjs:client connect: sending packet `connect` +1ms
  mqttjs:client _writePacket :: packet: {
  mqttjs:client   cmd: 'connect',
  mqttjs:client   protocolId: 'MQTT',
  mqttjs:client   protocolVersion: 4,
  mqttjs:client   clean: true,
  mqttjs:client   clientId: 'mqttjs_c8471ff3',
  mqttjs:client   keepalive: 60,
  mqttjs:client   username: undefined,
  mqttjs:client   password: undefined,
  mqttjs:client   properties: undefined
  mqttjs:client } +0ms
  mqttjs:client _writePacket :: emitting `packetsend` +1ms
  mqttjs:client _writePacket :: writing to stream +0ms
  mqttjs:client _writePacket :: writeToStream result true +10ms
...
  mqttjs:client writable stream :: parsing buffer +338ms
  mqttjs:client parser :: on packet push to packets array. +2ms
  mqttjs:client work :: getting next packet in queue +0ms
  mqttjs:client work :: packet pulled from queue +0ms
  mqttjs:client _handlePacket :: emitting packetreceive +1ms
  mqttjs:client _handleConnack +0ms
  mqttjs:client _setupPingTimer :: keepalive 60 (seconds) +0ms
  mqttjs:client connect :: sending queued packets +1ms
  mqttjs:client deliver :: entry undefined +0ms
  mqttjs:client _resubscribe +0ms
  mqttjs:client subscribe: array topic xyz +0ms
  mqttjs:client subscribe: pushing topic `xyz` and qos `0` to subs list +0ms
  mqttjs:client subscribe :: resubscribe true +0ms
  mqttjs:client subscribe :: call _sendPacket +0ms
  mqttjs:client _sendPacket :: (mqttjs_c8471ff3) ::  start +0ms
  mqttjs:client _writePacket :: packet: {
  mqttjs:client   cmd: 'subscribe',
  mqttjs:client   subscriptions: [ { topic: 'xyz', qos: 0 } ],
  mqttjs:client   messageId: 22413
  mqttjs:client } +0ms
  mqttjs:client _writePacket :: emitting `packetsend` +1ms
  mqttjs:client _writePacket :: writing to stream +0ms
  mqttjs:client _writePacket :: writeToStream result true +0ms
  mqttjs:client _writePacket :: invoking cb +0ms
  mqttjs:client noop :: undefined +0ms
  mqttjs:client writable stream :: parsing buffer +75ms
  mqttjs:client parser :: on packet push to packets array. +0ms
  mqttjs:client work :: getting next packet in queue +0ms
  mqttjs:client work :: packet pulled from queue +0ms
  mqttjs:client _handlePacket :: emitting packetreceive +0ms
  mqttjs:client _handleAck :: packet type suback +0ms
  mqttjs:client publish :: message `{"message":"CURRENT DT:2024-04-05T13:22:21.332Z"}` to topic `xyz` +1ms
  mqttjs:client publish :: qos 0 +0ms
  mqttjs:client MqttClient:publish: packet cmd: publish +0ms
  mqttjs:client _sendPacket :: (mqttjs_c8471ff3) ::  start +0ms
  mqttjs:client _writePacket :: packet: {
  mqttjs:client   cmd: 'publish',
  mqttjs:client   topic: 'xyz',
  mqttjs:client   payload: '{"message":"CURRENT DT:2024-04-05T13:22:21.332Z"}',
  mqttjs:client   qos: 0,
  mqttjs:client   retain: false,
  mqttjs:client   messageId: 0,
  mqttjs:client   dup: false
  mqttjs:client } +0ms
  mqttjs:client _writePacket :: emitting `packetsend` +0ms
  mqttjs:client _writePacket :: writing to stream +0ms
  mqttjs:client _writePacket :: writeToStream result true +0ms
  mqttjs:client _writePacket :: invoking cb +0ms
  mqttjs:client noop :: undefined +0ms
  mqttjs:client _sendPacket :: (mqttjs_c8471ff3) ::  end +0ms

BTW FYI, when I publish an event from AWS Console, nothing gets added to these logs.

[adrians5j]

Just wanted to add that I've also posted the same question on AWS re:post, in case this is maybe related to AWS, which I believe is more the case.

[robertsLando]

unfortunately I don't see anything wrong from your logs. YOu may get more logs by using DEBUG=mqtt* as that prints also mqtt-paket logs

[adrians5j]

Will try, thank you!! Adrian S.

…

On Fri, 5 Apr 2024 at 16:21, Daniel Lando ***@***.***> wrote: unfortunately I don't see anything wrong from your logs. YOu may get more logs by using DEBUG=mqtt* as that prints also mqtt-paket logs — Reply to this email directly, view it on GitHub <#1836 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABHCI7EMNRBDT75F7FB2QVDY32XOPAVCNFSM6AAAAABFZEJUAKVHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TAMRSGMZDK> . You are receiving this because you were mentioned.Message ID: <mqttjs/MQTT .***@***.***>

[adrians5j]

Just wanted to conclude this discussion by saying that I've found the issue. It was related to AWS Lambda function / authorizer, which did not return all of the needed IAM permissions. Once I fixed those, everything started working as expected.

More info here.