Esp8266 Code

esp01.ino

#include <ESP8266WiFi.h>

char ssid[] = "demowifi";   //  network SSID (name) 
char pass[] = "demowifi";   //  network password

//serial comm variables
uint8_t dataToSend = 0;
char dataFromAtmega[30];

WiFiServer server(80);
void setup() {
  Serial.begin(9600); 
  WiFi.mode(WIFI_STA); 
  WiFi.begin(ssid, pass); 

  while (WiFi.status() != WL_CONNECTED){ 
    delay(500);}     
server.begin();
}

void commWithAtmega(){
  
  Serial.print(dataToSend);
  while(!Serial.available());

  if(Serial.available())
     Serial.readBytesUntil('#',dataFromAtmega,30); //reads the input until "#"  and stores it in the data array.
    

  }

void loop() {
  
  WiFiClient client = server.available();
  if (client)
  {
    if (client.connected())
    {
      delay(10);
      if(client.available())
      {
        dataToSend = client.parseInt();
        client.flush();
        commWithAtmega();
        client.print(F("HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r\n"));
        client.println(dataFromAtmega);
    
      }
      }
    delay(1); 
    client.stop();
    
  }
  }