AskSensors IoT Platform Documentation

Connect Hardware to AskSensors over MQTT

AskSensors MQTT Summary:

1-MQTT Publish/Subscribe API

2-Connect ESP8266 over MQTT

3-Connect ESP32 over MQTT

4-Connect Arduino Ethernet over MQTT

4-Connect Arduino Ethernet over MQTT

The following guide shows how to publish data to the AskSensors IoT platform using Arduino Ethernet shield and MQTT.

a) Prerequisites :
b) Required Hardwares :
  • Computer running Arduino software (version 1.8.7 or higher).
  • Arduino Uno.
  • Arduino Ethernet Shield
  • USB micro cable to connect the ESP8266 board to the computer.
  • RJ45 Ethernet Cable

c) Software :
The provided code includes the libraries for both connecting to a Ethernet network and to publish data to AskSensors using MQTT.
You need to fill the following:

  • The Api Key In and username to set the MQTT Topic:username/apiKeyIn
  • A fixed IP address.
  •   const char* username = "................."; // my AskSensors username
      const char* pubTopic = "......./....."; // username/apiKeyIn
      IPAddress ip(..., ..., ..., ...); // IP address

d) Run the code:
  • Connect your Arduino board to the computer via serial USB and upload the code using the Arduino IDE.
  • Connect your Arduino Ethernet shield to the network through Ethernet cable
  • Reset the board
  • Return back to your sensor page on AskSensors, Click on'Show Graph' and select the chart type (such as Line, Bar, Binary..) to visualize your sensor data stream in graph.
  • Open a serial terminal. You can cross-check the AskSensors graph readings with the values being printed on your Arduino Terminal.
e) Source Code :
A basic source code is shown below. Please refer to the AskSensors Github page to get the latest version and updates.
* MQTT and AskSensors IoT Platform
* Description: Arduino Ethernet publishes data to AskSensors using MQTT
* Author:, 2019
* github:
#include <SPI.h>
#include <Ethernet.h>
#include <PubSubClient.h>
// TODO: AskSensors MQTT user config
const char* username = "................."; // my AskSensors username
const char* pubTopic = "............/.................."; // username/apiKeyIn
const unsigned int writeInterval = 25000; // write interval (in ms)
// MQTT host config
const char* mqtt_server = "";
unsigned int mqtt_port = 1883;
// ETHERNET config.
// Enter a MAC address for your controller below.
// Newer Ethernet shields have a MAC address printed on a sticker on the shield
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
// Set the static IP address to use if the DHCP fails to assign
IPAddress ip(..., ..., ..., ...); // TODO: Add the IP address
EthernetClient askClient;
PubSubClient client(askClient);
void setup() {
  Serial.println("********** Program Start : Arduino Ethernet publishes data to AskSensors over MQTT");
  Serial.print("********** connecting to Ethernet : ");
   // start the Ethernet connection:
  if (Ethernet.begin(mac) == 0) {
     Serial.println("Failed to configure Ethernet using DHCP");
    // try to congifure using IP address instead of DHCP:
     Ethernet.begin(mac, ip);
  // give the Ethernet shield a second to initialize:
  client.setServer(mqtt_server, mqtt_port);

void loop() {
  if (!client.connected())
  Serial.println("********** Publish MQTT data to ASKSENSORS");
  char mqtt_payload[30] = "";
  snprintf (mqtt_payload, 100, "m1=%ld&m2=%ld", random(10,100), random(10,100) );
  Serial.print("Publish message: ");
  client.publish(pubTopic, mqtt_payload);
  Serial.println("> MQTT data published");
  Serial.println("********** End ");
  delay(writeInterval);// delay
void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("********** Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect("ethClient",username, "")) {
      Serial.println("-> MQTT client connected");
    } else {
       Serial.print("failed, rc=");
      Serial.println("-> try again in 5 seconds");
      // Wait 5 seconds before retrying

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