Client Server Communication over CoAP Protocol : IOT Part 33

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//Program to 


/*

  @Project: Browser_client_controls_Server_light

  

  @Hardware used:

     ESP8266-01

     CP2102 or Arduino UNO (as a USB to Serial converter)

     LED & 220E resistor

     External Power supply to provide 3.3V to ESP8266 (Optional)

       

  @Brief Introduction: 

      In this application, we have used ESP8266 as our CoAP server & Copper (Cu) as a CoAP client
 (it is supported with mozilla firefox browser.)

      The client sends GET, PUT request to the server and server controls the light on the 
basis of receiving PUT message.

      For more details, please refer our Article: Browser client controls Server light

*/


//Include Libraries

#include          //Include the ESP8266 library to connect the server to the WIFI

#include             //Include the CoAP server library to connect the server using CoAP protocol


/*

 * Callback Function Declaration: This is a callback function, whenver server receives any get or put request, 

 * the server responses accordingly through this function.

 * This Function takes the packet (Message), IP address & port of the CoAP client & observe the request on
 the particular service.

 */

void Light_control(coapPacket &packet, IPAddress ip, int port, int obs);


//Create an instance of CoAP server

coapServer coap;


/*

 * Access point SSID & PASSWORD

 * Change this according to the network

  */

const char* SSID_of_Router = "NOT UR WIFI";

const char* PASSWORD_of_Router = "marketing";


//Connect LED to the GPIO2 of ESP8266 & for reading the led state at the client end,
 initialize the Variable for it.

int light = 2;

bool Light_state;


//Define the Callback function

void light_control(coapPacket *packet, IPAddress ip, int port, int obs) {


  char p[packet->payloadlen + 1];

  memcpy(p, packet->payload, packet->payloadlen);

  p[packet->payloadlen] = NULL;

  Serial.println(p);


  String message(p);


  if (message.equals("0"))

  {

    digitalWrite(light, LOW);

    Serial.println("light is OFF");

  }

  else if (message.equals("1")) {

  

    digitalWrite(light, HIGH);

    Serial.println("light is ON");

  }

  

  char *Room_light = (digitalRead(light) > 0) ? ((char *) "1") : ((char *) "0");


  //The server look for the observe flag or GET request from the client

  if (obs == 1){

    coap.sendResponse(Room_light);

    }

  else{

    coap.sendResponse(ip, port, Room_light);

    }

}


void setup() {

  yield();

  

  //Start the serial Monitor at specified baud Rate as ESP8266 needs 115200 buad
 rate to communicate using serial

  Serial.begin(115200);


  //Initiate the connection of ESP8266 to the Router

  WiFi.begin(SSID_of_Router, PASSWORD_of_Router);

  Serial.println(" ");

  Serial.print("Connecting to...... ");

  Serial.println(SSID_of_Router);


  //Wait for the connection establishment

  while (WiFi.status() != WL_CONNECTED) {

    yield();

    Serial.print(".");

  }

  Serial.println("");

  

  //If ESP8266 Wi-Fi is connected to the Router then 

  //we will see the IP address assigned to the ESP8266

  Serial.println("WiFi connected");

  Serial.println(WiFi.localIP());


  

  pinMode(light, OUTPUT);

  digitalWrite(light, HIGH);

  Light_state = true;


  // add server url endpoints.

  // We can add multiple endpoint urls.

  coap.server(light_control, "Room_light");


  //Initiate the Connection of ESP8266 as a CoAP server & the port on 
which server is listening.

  coap.start();

  coap.start(1234);

}


void loop() {

  coap.loop();

  delay(1000);

}


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