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.

Filter by
Sorted by
Tagged with
1
vote
0answers
22 views

ESP8266 How to run MQTT Client and Http Client in one loop

Scenario: Existing project: read soft serial then do http post New project: MQTT player from other (MrDIY / MrDIY Audio Notifier · GitLab) Objective: Combine together (Result: successful ) Issue: When ...
0
votes
0answers
16 views

How to correctly use SSL certs with the Adafruit SIM800H

I am trying to use a Adafruit Sim800H to connect to Azure using MQTT with an SSL certificate. My first step is trying to put a new SSL certificate onto the board. To do this I am using this example ...
2
votes
1answer
70 views

ArduinoJson library parsing error

I am trying to retrieve JSON mqtt message I received in ESP32. void mqttMsgCallback(char* topic, byte* payload, unsigned int length) { payload[length] = '\0'; String _message = String((char*)...
2
votes
1answer
200 views

OTA over MQTT for ESP32

Before starting working, I am just researching around how can I achieve OTA over MQTT in ESP32 in using Arduino IDE. The process I understand the esp listen to MQTT messages and then received that ...
1
vote
0answers
40 views

How to get the value of a measurement transmitted by a BLE device?

I would like to use a BLE temperature sensor (such as the Inkbird IBS-TH1 Mini BLE Sensor), however, I want to be able to display the temperature measurements in my own website. To do this I am ...
1
vote
0answers
42 views

Is it possible to upload a private root certificate to an Arduino Nano33?

I'm trying to connect an Arduino Nano 33 to an mqtt broker with TLS authenticaton on the broker side. To do that I need my Arduino board to have access to the the root certificate. My understanding is ...
1
vote
0answers
74 views

Multiple MQTT topics

I have 3 nodemcu's(ESP32) each connected with a sensor, from which I get data and send it to aws IoT-core. How can I send all 3 sensor's data by a single MQTT subscription? The below code is for a ...
3
votes
1answer
271 views

Connect ESP32 via MQTT

For a project I am working on, I need to connect my ESP32 board to another server via MQTT protocol. I am using the Mosquitto MQTT Broker and it is presently on my laptop. Following is the test code I ...
1
vote
1answer
116 views

Message parsing from MQTT server

I'm making a NodeMCU based home automation. I adapted code I found on internet for controlling a device (say LED) via MQTT broker hosted on a Raspberry Pi. It works fine. But when I try to scale it up ...
1
vote
0answers
134 views

How to avoid MQTT reconnect Loop

I have the following code designed to allow me to control my device from my website using mqtt broker while internet is available. I also built in a local webserver to control the device in case of ...
0
votes
1answer
58 views

I Can't Connect to my MQTT server via arduino

I have mosquitto MQTT installed on my VPS server which I can subscribe and publish to it using paho client thorugh websockets. However when I tried to connect to it through Arduino, I get the ...
0
votes
1answer
374 views

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 ...
0
votes
2answers
1k 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 ...
1
vote
0answers
26 views

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:...
2
votes
1answer
64 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 ...
0
votes
0answers
21 views

no readings from topic MQTT

I have setup two arduinos, one supposed to fetch data from my website and feed it to a topic. The other board supposed to subscribed to that same topic and reads fetched data I was able to get data ...
0
votes
1answer
92 views

Modbus TCP together with MQTT over same ethernet

I'm currently in a planning phase for a project. I want to read some sensor data over Modbus TCP, do some simple calculations on the Arduino and publish the results over MQTT. Which means I have 2 RJ-...
1
vote
0answers
184 views

Arduino Uno + NodeMCU serial to MQTT

I made a pool monitor with ORP + pH + temp sensor. I had everything working (apart from ORP sensor causing interference with pH sensor, but that is a different topic...) for the past couple days in a ...
0
votes
1answer
480 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 ?
1
vote
0answers
34 views

how to serially off leds in an esp running mqtt

hi im using at tiny 85 to monitor dc switches and to serial print with this code below to esp8266 with local broker to turn leds on and off but its only working through mqtt but not with physical ...
0
votes
1answer
109 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(...
0
votes
2answers
125 views

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"); }...
1
vote
0answers
315 views

node mcu disconnect from mqtt server

/* Basic ESP8266 MQTT example This sketch demonstrates the capabilities of the pubsub library in combination with the ESP8266 board/library. It connects to an MQTT server then: - ...
1
vote
1answer
1k views

Convert JSON into string for MQTT

I am trying to publish json object into string with following snippet JSONVar data; data["chipid"] = chipId; data["co2_equivalent"] = co2_equivalent.c_str(); data["tvoc"] = tvoc.c_str(); data["...
3
votes
2answers
5k views

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 = "...
1
vote
0answers
133 views

How to edit code from Node-Red to Cayenne

I am working on a project to run some (relays or LED's) on an inputs (Pins) Arduino by esp8266-01s . now while searching on internet I found a video divided it two step that talks about the issue ...
1
vote
2answers
5k views

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" #...
1
vote
0answers
99 views

How to set ALPN ProtocolName when negotiating SSL using ArduinoBearSSL

I am trying to set up an Arduino MKR Wifi 1010 to push MQTT messages to AWS IOT. I am following this tutorial https://create.arduino.cc/projecthub/Arduino_Genuino/securely-connecting-an-arduino-mkr-...
0
votes
1answer
182 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 ...
1
vote
0answers
2k views

esp32 arduino wifi disconnect

I have this code running on ESP32 connected to SVM30-J #include <WiFi.h> #include <PubSubClient.h> #include <Arduino_JSON.h> #include <svm30.h> // Replace the next variables ...
1
vote
0answers
334 views

ESP8266 mqtt publish + subscribe + serial read

seems I have some issues in my code as I subscribe for specific mqtt topic and also read same value via serial and publish it to mqtt. It takes time for device connected to serial to change setting ...
0
votes
1answer
2k 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' ...
0
votes
1answer
41 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 ...
0
votes
1answer
677 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 ...
1
vote
0answers
637 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/...
1
vote
1answer
49 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 ...
1
vote
1answer
3k views

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"] = ...
2
votes
1answer
305 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 ...
1
vote
1answer
296 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 ...
0
votes
1answer
354 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 ...
1
vote
1answer
1k 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....
0
votes
1answer
468 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 ...
0
votes
1answer
595 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 ...
2
votes
2answers
354 views

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 ...
1
vote
0answers
663 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 ...
1
vote
2answers
396 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 ...
2
votes
3answers
7k views

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 ...
1
vote
0answers
41 views

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 ...
1
vote
1answer
888 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 ...
0
votes
1answer
457 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 ...