Arduino to PC Commmunicaton over Ethernet Technology and MQTT Protocol

#include<SPI.h>                                                             //include library for serial communication

#include<Ethernet.h>                                                        //include library for Ethernet communication

#include <PubSubClient.h>                                                   //include library for MQTT pub sub protocol

#include <DHT.h>                                                            //include library for Temperature sensor 


#define DHTPIN  7                                                            //DHT temperature sensor connected to pin 7

#define DHTTYPE DHT11                                                       //TYPE of DHT 11 or 22

DHT dht(DHTPIN, DHTTYPE);                                                   //Create the instance of DHT


#define ledPin 2                                                            //led connected to pin 2

char* tempC;                                                                //Variable to hold the temperature of the hall

char message_buffer[100];                                                   //initialize a buffer for incoming temperature values                                     


byte mac[]= {0x00, 0xAA, 0xBB, 0xCC, 0xDD, 0xEF};                           //MAC address of your unique Arduino device

IPAddress ip(192,168,1,111);                                                //IP address of the Arduin Etherent shield        

const char* mqtt_server = "broker.mqtt-dashboard.com";                      //The broker or server domain name


EthernetClient ethClient;                                                   //Create an Ethernet Client class to connect to the MQTT server.

PubSubClient client(ethClient);                                             //create the MQTT client objects  


int timer1_count = 46874;                                                  //Timer1-16 bit, Required time = 3 sec, F_CPU= 16MHz


void timer1_init()

{

   //Initialize registers 

   TCCR1A = 0;                                                             //set entire TCCR1A register to 0

   TCCR1B = 0;                                                             //set entire TCCR1B register to 0

  

   //Initialize counter

   TCNT1 = 0;

   

   // Set the Compare value that

   // was calculated for generating a Delay Time period 

   // This updates the temperature after every Delay Time Period

   OCR1A = timer1_count;

    

   //Start timer1                                                                                       

   //Set up timer with prescaler = 1024 and CTC mode

   TCCR1B |= (1 << WGM12)|(1 << CS12)|(1 << CS10);    

}



void setup() {

  

   pinMode(ledPin,OUTPUT);                                      //configure the led pin as OUTPUT

   Serial.begin(115200);                                        //Set the baudrate of ESP8266 to show the process on serial monitor

   Ethernet.begin(mac, ip);                                     //Start the Ethernet communication   

   dht.begin();                                                 //start the dht sensor to sense temperature


   timer1_init();                                              //Initialize the timer function

   

   //By setting server and messgae callback function, the client is ready to use 

   client.setServer(mqtt_server, 1883);

   client.setCallback(Received_Message);

}


/*

* Function name = Received_message

* Client receives the message and functions accordingly

* Input parameter = Topic, Payload and message length

* Output parameter = void

*/

void Received_Message(char* topic, byte* payload, unsigned int length) {

   Serial.print("Message arrived [");

   Serial.print(topic);

   Serial.print("] ");

   for (int i = 0; i < length; i++) {

    Serial.print((char)payload[i]);

  }

  

   // Handle the message we received 

   // Here, we are only looking at the characters of the received message (payload[0])

   // If it is on, turn the led will be on.

   // If it is off, turn the led will be off.

   if((char)payload[0] == 'o' && (char)payload[1] == 'n') //on

    digitalWrite(2,HIGH);

  else if((char)payload[0] == 'o' && (char)payload[1] == 'f' && (char)payload[2] == 'f') //off

    digitalWrite(2,LOW);

    

  Serial.println();

}


/*

* Function Name = Reconnect

* To establish the connection of Ethernet with MQTT broker 

* and Will publish and subsribe to the topic

*/

void reconnect() {

   // Loop until we're reconnected

   while (!client.connected()) {

    Serial.print("Attempting MQTT connection...");

     //Attempt to connect

     if (client.connect("ethClient")) {

      Serial.println("connected");

      //and resubscribe

      client.subscribe("Ethernet/LED_status");

    } 

  else {

      Serial.print("failed, rc=");

      Serial.print(client.state());

      Serial.println(" try again in 5 seconds");

      // Wait 5 seconds before retrying

      delay(5000);

    }

  }

}



void loop() {

  //When Ethernet client will be connected to the broker, 

  //then call the function reconnect and publish and subscribe the data from broker.

  if (!client.connected()) {

    reconnect();

  }

  client.loop();


   float tempF = dht.readTemperature();                   //Read the temperature from DHT sensor

   

   //There is a useful c function called dtostrf() which will convert a float to a char array so it can then be printed easily.  

   //The format is: dtostrf(floatvar, StringLengthIncDecimalPoint, numVarsAfterDecimal, charbuf);

   tempC = dtostrf(tempF,5,2,message_buffer);

      

      // check whether the flag bit is set

     // if set, it means that there has been a compare match

     // and the timer has been cleared

     // use this opportunity to publish the temperature value

      if(TIFR1 & (1 << OCF1A))

      {

      //publish the temperature value

      client.publish("current_temperature", tempC);

      }

      

      // wait! we are not done yet!

      // clear the flag bit manually since there is no ISR to execute

      // clear it by writing '1' to it (as per the datasheet)

      TIFR1 |= (1 << OCF1A);

}

Demo: