The following tutorial show you how you can send temperature and humidity data measured by DHT11 sensor connected to a nodeMCU / ESP8266 board with MQTT message. The messages are displayed in the WEB MQTT interactive MQTT web client dashboard with the gauge and chart UI elements.
https://rundebugrepeat.com/webmqtt/

The following DHT11 library used:
https://github.com/adafruit/DHT-sensor-library
Source code:
/*
Basic ESP8266 / NodeMCU MQTT example using the pubsub client library
In this example a DHT11 temperature/humidity sensor is connected to the nodeMCU/ESP8266 board
The following measurement data will be sent to the following paths:
temperature [°C] -> rundebugrepeat/test/dht11/temp_celsius
temperature [°K] -> rundebugrepeat/test/dht11/temp_fahrenheit
humidity [%] -> rundebugrepeat/test/dht11/humidity
To install the ESP8266 board, (using Arduino 1.6.4+):
- Add the following 3rd party board manager under "File -> Preferences -> Additional Boards Manager URLs":
http://arduino.esp8266.com/stable/package_esp8266com_index.json
- Open the "Tools -> Board -> Board Manager" and click install for the ESP8266"
- Select your ESP8266 in "Tools -> Board"
*/
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include "DHT.h"
#define DHT11PIN 4 //on the NodeMCU board it is the D2 PIN!
//for more information about Nodemcu PINOUT
//https://rundebugrepeat.com/nodemcu/
#define DHTTYPE DHT11
DHT dht(DHT11PIN, DHTTYPE);
// Update these with values suitable for your network.
const char* ssid = "..........."; //Wifi SSID
const char* password = "............"; //WIFI password
const char* mqtt_server = "mqtt.eclipse.org"; //MQTT Broker address
const int mqtt_port = 1883; //MQTT broker port
WiFiClient espClient;
PubSubClient client(espClient);
void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
randomSeed(micros());
Serial.println("");
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
}
void callback(char* topic, byte* payload, unsigned int length) {
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("]: ");
char message[length];
for (int i=0; i< length; i++){
message[i] = (char)payload[i];
}
Serial.println(message);
}
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
// Create a random client ID
String clientId = "ESP8266Client-";
clientId += String(random(0xffff), HEX);
// Attempt to connect
if (client.connect(clientId.c_str())) {
Serial.println("Connected!");
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}
void setup() {
Serial.begin(115200);
dht.begin();
setup_wifi();
client.setServer(mqtt_server, mqtt_port);
client.setCallback(callback);
}
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.readHumidity();
// Read temperature as Celsius (the default)
float t = dht.readTemperature();
// Read temperature as Fahrenheit (isFahrenheit = true)
float f = dht.readTemperature(true);
// Check if any reads failed and exit early (to try again).
if (isnan(h) || isnan(t) || isnan(f)) {
Serial.println(F("Failed to read from DHT sensor!"));
return;
}else{
/*
* Publish the measured data:
* temperature [°C] -> rundebugrepeat/test/dht11/temp_celsius
* temperature [°K] -> rundebugrepeat/test/dht11/temp_fahrenheit
* humidity [%] -> rundebugrepeat/test/dht11/humidity
*/
client.publish("rundebugrepeat/test/dht11/temp_celsius",String(t).c_str());
client.publish("rundebugrepeat/test/dht11/temp_fahrenheit",String(f).c_str());
client.publish("rundebugrepeat/test/dht11/humidity",String(h).c_str());
}
}