nodemcu_esptoesp

https://circuits4you.com/2018/01/01/esp-to-esp-communication/?fbclid=IwAR1UKu_-35_d9wk4rSJEaj5M4ty_tiWUw3rLHR-mmP8Vnq3LwqvuVvjeQ4c

this tutorial we will make two ESP8266 as wireless serial (chat application) using UDP communication protocol. You can have communication between multiple ESPs at the same time. We are using UDP broadcast. UDP is unreliable, but works for many application. UDP gives advantage of sending one message to all ESP8266 devices on same network at the same time using broadcast.

In this post I will explain two types of ESP to ESP communication methods.

One ESP to another ESP communication

In this we make one ESP as Access point and another as Client which connects to access point and starts communication. This example is like chat using two ESPs.

ESP8266 Code for ESP to ESP Communication

Access Point ESP Program

This ESP makes access point. Access point always have IP: 192.168.4.1

In this program I am using only one IP i.e. broadcast IP 192.168 43.255. Make sure your IP range and make last digits to 255.

Upload this program in All ESP8266. Change SendIP as per your network series. Give your WiFi Router SSID and Password.

#include <ESP8266WiFi.h>

#include <WiFiUdp.h>

const char *ssid = "circuits4you.com";

const char *pass = "password";

unsigned int localPort = 2000; // local port to listen for UDP packets

IPAddress SendIP(192,168,43,255); //UDP Broadcast IP data sent to all devicess on same network

// A UDP instance to let us send and receive packets over UDP

WiFiUDP udp;

char packetBuffer[9]; //Where we get the UDP data

//======================================================================

// Setup

//=======================================================================

void setup()

{

Serial.begin(9600);

Serial.println();

WiFi.begin(ssid, pass); //Connect to access point

Serial.println("");

// Wait for connection

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

delay(500);

Serial.print(".");

}

Serial.println("");

Serial.print("Connected to ");

Serial.println(ssid);

Serial.print("IP address: ");

Serial.println(WiFi.localIP());

//Start UDP

Serial.println("Starting UDP");

udp.begin(localPort);

Serial.print("Local port: ");

Serial.println(udp.localPort());

}

//======================================================================

// MAIN LOOP

//======================================================================

void loop()

{

int cb = udp.parsePacket();

if (!cb)

{

//If serial data is recived send it to UDP

if(Serial.available()>0)

{

udp.beginPacket(SendIP, 2000); //Send Data to Master unit

//Send UDP requests are to port 2000

char a[1];

a[0]=char(Serial.read()); //Serial Byte Read

udp.write(a,1); //Send one byte to ESP8266

udp.endPacket();

}

}

else {

// We've received a UDP packet, send it to serial

udp.read(packetBuffer, 1); // read the packet into the buffer, we are reading only one byte

Serial.print(packetBuffer);

delay(20);

}

}

Results of Multiple ESP communication

I sent 123456789 from one ESP to another, Few numbers are missed as I said earlier UDP is unreliable. You can clearly see missing data packets. Its useful when you send data multiple times and have some feedback mechanism. This way you can have esp to esp communication.