Questions tagged [mqtt]

MQTT (Message Queuing Telemetry Transport) is a machine-to-machine (M2M)/"Internet of Things" connectivity protocol. The MQTT protocol enables a publish/subscribe messaging model in an extremely lightweight way. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium.

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MQTT over serial

I'm planning to build a 32 relay IOT node next to my Raspberry Pi. The relays will be controlled by an Arduino Mega 2560. The Pi will run Home Assistant and Mosquitto so I would prefer to communicate ...
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1answer
38 views

MQTT connection not being recognised in void loop()

I am trying to publish MPU 9250 readings in the Adafruit IO sending the data from ESP32. The WiFi connection is being established, but the code is not going inside the if(mqtt.connected()) inside the ...
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Connecting to MQTT causes DHT11 Sensor to stop working?

I have a project I am working on, based on an ESP32 from NodeMCU. I have a bunch of sensors connected to said ESP32 - they all work and the code itself "works" with a minor quirk. The issue in ...
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How to connect to MQTT broker with TLS?

I have ESP8266 which is connecting to MQTT broker and it is working ok using user+pass with following code: #include <ESP8266WiFi.h> #include <PubSubClient.h> const char* ssid = "...
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1answer
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publish json data to mqtt

I am trying to publish JSON data to mqtt with following code snippet #include <Arduino_JSON.h> JSONVar data; data["temperature"] = temperature; data["humidity"] = humidity; data["pressure"] = ...
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MQTT bridging with Arduino and ESP8266 - What software should I use?

Sorry for the vagueness in my question, I am just looking for ideas to point me in the correct direction please... I wish to connect many (read: 20+) different sensors to a local wifi network and ...
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ESP8266 MQTT client error

#include <PubSubClient.h> #include <ESP8266WiFi.h> //EDIT THESE LINES TO MATCH YOUR SETUP #define MQTT_SERVER "YOUR.MQTT.SERVER.IP" const char* ssid = "YOUR_SSID"; const char* password = "...
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3answers
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Convert byte* to int in Arduino

I am trying to convert byte* value to int here is how I have it. void mqttCallback(char* topic, byte* payload, unsigned int length) { String topicStr = topic; int* payload_value; int ...
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760 views

Mosquitto TLS over WifiMulti on ESP8266

With these few lines I am able to attach my certificate, tell it to WifiClientSecure the certificate, start the wifi as well as the mosquito pubsubclient: WiFiClientSecure espClient; WiFi.begin(ssid, ...
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723 views

Using MQTT to send time stamp - to Arduino

In previous question in this forum - I asked about updating clock on an ESP8266, using MQTT broker to send a time stamp on demand, in following manner: 1) ESP8266 sends a publish containing the ...
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ESP8266 fail to connect MQTT broker

I am using NodeMCU dev board with ESP8266 WIFI. Every time I try to connect to my local broker it returns this error: failed, rc=-2 try again in 5 seconds I am using Ubuntu 18.04, my local brokers ...
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230 views

Publish chipid to mqtt using ESP32-CAM

I have been trying to push the data of temp, humidity, and pressure from a sensor to MQTT using ESP 32Cam, and was able to do using the following code: pressure = bme.readPressure(); //Convert the ...
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1answer
729 views

Impossible to connect ESP32 with Mosquitto on Raspberry using certificates

I installed Mosquitto broker in Raspberry in my local network. I generated certificates in Raspberry as follows: sudo openssl genrsa -out ca.key 2048 sudo openssl req -new -x509 -days 3600 -key ca....
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1answer
673 views

Notoriously unstable ESP8266 MQTT-client

I am doing a project where an ESP8266 receives data from an Arduino Uno and publishes it via MQTT. After a random amount of time, it will stop sending data to my MQTT broker. It might be an hour, it ...
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1answer
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ESP8266 deep sleep and MQTT

I am working on a project were I am putting my board into deep sleep mode, and it wakes up with an interrupt from a sensor. When it wakes from deep sleep I would like to send a message to my MQTT ...
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1answer
906 views

Use MQTT to update internal clock

I write code to upload to ESP8266. I wish to use time stamp in order to log events. I found an NTP sketch, I can work with ( since it has a wifi connection ), but I wish to keep my code as simple as ...
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1answer
54 views

couldn't connect to MQTT broker via esp8266/32 and pub/sub client

I want to use hiveMQ public broker in my project that's the same broker as what available in PubSubClient esp8266 examples but when I change WiFi SSID and password in example and upload it I got this ...
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Mosquitto doesn't work after reboot [closed]

When i restart my raspberry pi 4 and check for mosquitto status it brings to me active: failed it seems to be it works for just the first time when i setup it all i need is to communicate esp32 with ...
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4004 (NOT_FOUND) ON MQTT

I tried to send random data to MQTT but it's not working and I get: { "m2m:rsp" : { "rsc" : 4004, "rqi" : "123456", "pc" : "Resource not found", "to" : "5a185cedc6ad749b:...
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1answer
51 views

ESP32 using PubSub, creating an error when implemted inside a library

I wish to combine into a single library Wifi + MQTT, for a multi devices project. right after boot, getting Wifi - I get an error the moment MQTT server is trying to connect: mqttClient.connect(...
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367 views

How to parse data most efficiently coming through mqtt with ESP8266

I am writing a program that is currently set up like so: Python script running on my computer. Raspberry pi is the broker for the mqtt data transmission An ESP8266 is programmed to listen to/...
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1answer
168 views

ESP8266 Arduino MQTT callback with dynamic topics

I have a program that depending on user input, it creates one or several objects that will publish data to a MQTT broker, each one with a different topic. This is already done. The ESP8266 also has ...
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538 views

MQTT subscribe callback fails to be called in ESP8266 deepsleep mode

Refer to ESP8266 deep sleep and MQTT I executed the code in the given link. However i am not able to receive the subscribe message that are send from MQTT test broker(MQTT Lens) on the serial ...
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2answers
336 views

How to get a list of IPs in a LAN using NodeMcu?

I'm going to create an IoT system. I use a Raspberry Pi as a MQTT broker and as a webserver. Every day, the Pi gets a new IP address, so I need to find its new IP address via ESP8266 to use this ...
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Arduino clients suddenly not able to connect (or publish) to MQTT

we are struggling with a project that has things (arduinos as clients) communicating to our MQTT broker (mosquitto) running on a DigitalOcean droplet (inside a docker). We have about 200 things at ...
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127 views

I can't send GPS data to server

I am trying to send gps location data every 3 seconds to mqtt server if it's updated but my device shows weird stack errors and resets. What i am missing? I am using tinygps++ and pubsubclient as ...
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253 views

Real-time Pub/Sub thru MQTT between JoyStick and OnBoard Drive units [both ESP8266] - Connection issues

I looked around for solutions to my issue by searching on the forum and elsewhere and haven't seen similar issues - (https://arduino.stackexchange.com/search?page=2&tab=Relevance&q=MQTT%...
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ESP8266 MQTT periodically disconnecting

I use an MQTT to communicate with an ESP8266. I'm using cloudmqtt.com and PubSubClient. Sometimes the ESP disconnects from the MQTT and reconnects. I checked the log from cloud and I got this data ...
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529 views

Soft WDT with HX711 and PubSubClient libraries

I'm using NodeMCU 0.9 My sketch crashes if the following 2 include are present in the sketch: #include <PubSubClient.h> #include <HX711.h> I obtain a Soft WDT reset If I do not use ...
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3answers
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ESP-01 not waking correctly up after deep sleep

I have an ESP-01 that I want to measure pool temperature with. It will send the data over MQTT to the broker. I have connected RST to GPIO16 so I can use the deep sleep functionality. Currently I am ...
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1answer
184 views

How can I call the constructor of a Class after it called once? [closed]

I have a problem with Classes. I have a bunch of code, that code is uses Adafruit MQTT FONA library. I call the Class for make new Instance and Connect to specified server with this code; ...
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1answer
2k views

MQTT not working on ESP8266 (Nodemcu 0.9)

I'm trying to use NodeMCU on my ESP8266 (NodeMCU 0.9) but the board keep crashing and I don't understand why. I tested the mqtt broker using command line and it works perfectly, so I can suppose that ...
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esp32-cam publish image to mqtt

I want to publish image capture through ESP32-CAM to MQTT. Have following code : #include "WiFi.h" #include "esp_camera.h" #include "esp_timer.h" #include "img_converters.h" #include "Arduino.h" #...
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1answer
412 views

MQTT on nano with Ethernet shield not working

I'm using an arduino nano with an ethernet shield (ENC28J60), and ethernet eem to be working (I can create a webserver with Ethercard library).However, i'm stuck when i try to connect to a MQTT ...
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1answer
327 views

Mqtt not subscribe on topic that's converted from String to char array

I am still not sure what should be the exact Title for this question, because I don't know where the problem is. I am using #include <MQTTClient.h> mqtt library to subscribe on a topic. This ...
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1answer
582 views

String & Char concatenations

A newbie in Arduino- and I'm trying to concatenate string and chars ( well in python it is quite different ). I'm trying to post a MQTT message- constructed following format to the client.publish(...
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1answer
134 views

PubSubClient - MQTT_MAX_PACKET_SIZE How is it calculated

I'm using an ESP32, and I want to rule out a probable MQTT error. In PubSubClient , MQTT_MAX_PACKET_SIZE is set to 256. Is 256 the size for message only ? if not, what is left for message only ?
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writing mqtt payload to spiffs file

I'm trying to write the payload of a MQTT message into a file in the SPIFFS file system of my esp32 board. I've tried this: if(file.print((long)payload)) { Serial.println("File was written"); }...
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1answer
120 views

How to transmit data from Arduino to Raspberry Pi?

I am planning to build a network with five Arduino Mega devices, each of which will collect data using multiple sensors. Each Arduino will periodically transmit the sensor data to a gateway Raspberry ...
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1answer
1k views

cast from 'char*' to 'char' loses precision

Bit of a noob here. Im trying to use the sensor number (float) in my mqtt topic, but cant seem to get this right. Any help would be appreciated. Keep getting this error (cast from 'char*' to 'char' ...
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1answer
36 views

How to execute commands over desired amount of time

I have a program that receives 4 commands on 4 channels to change the color of an LED using mqtt communication. Lets just focus on two of the channels, the time and the red. I am sending a length of ...
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1answer
37 views

How do I change the scope of an object?

I am using the File/Examples/Adafruit MQTT Library/mqtt_ESP8266 example as a model for my code. In the example, the mqtt object is created as a global variable, and everything works fine. However, I ...
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1answer
223 views

Obtain retained MQTT message

I’m using ESP8266 with Arduino code. Each device posts a ‘state’ and an ‘avail’ messages for a specific topic. I wish to be able to read those retained messages and not only right after connecting ...
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1answer
312 views

Waking an ESP8266 from Light-Sleep using a signal from MQTT?

I was wondering if it would be possible to wake an ESP8266 from a request over MQTT while it is in Light-Sleep mode? I am planning to implement a smart switch that would receive messages from a ...
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1answer
440 views

MQTT PubSubClient connection problem with ESP32

I am experiencing some problems with string in Arduino application with ESP32. I don't understand why this code works: mqtt.setServer ("m20.cloudmqtt.com", port); //is OK and this does not work ...
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1answer
744 views

MQTT - Can lastwill be sent to multiple topics?

I'm using an ESP8266 as an IOT device, with MQTT to send status messages. Each device have its own availability topic, to state its online or offline state ( needed for Home Assistant indication on ...
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1answer
203 views

Arduino Uno - MQTT message using PUBSUB on ESP8266

I'm trying to write code involving MQTT messages to operate an ESP8266 relay ( a Sonoff device ), using PubSub library. For some, unknown for me, reason - messages larger than 99 chars are not sent. ...
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1answer
669 views

Unable to Configure MQTT Client ID using Adafruit MQTT Library

I am utilizing the MQTT library that Adafruit has created, located here, and the library itself works wonderfully - however I am finding myself unable to edit the Client ID or configure the PINGRESP. ...
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1answer
1k views

Arduino MQTT Bluetooth

Is there a library to use MQTT with a bluetooth module (HC-06) instead of WiFi? If not is there a similar ready for use implementation of a publisher subscriber pattern available?
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PubSubClient: Subscription working, but callback never called

I am using an ESP32 (https://heltec.org/project/wifi-kit-32/) with a AM2302 DHT22 and an LDR, talking to mosquitto on a Linux box. Publishing data is working fine, other than the "exceeded ...