// ESP8266+espnow-sender.ino
#include <ESP8266WiFi.h>
#include <espnow.h>
uint8_t receiverAddress[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

typedef struct struct_message {
  char nachricht[32];
} struct_message;

struct_message myData;

void OnDataSent(uint8_t *mac_addr, uint8_t sendStatus) {
 if (sendStatus != 0) 
   Serial.println("Delivery success");
}
 
void setup() {
  Serial.begin(9600);
  WiFi.mode(WIFI_STA);
  while (esp_now_init() != 0) {
    Serial.println("Error initializing ESP-NOW");
    delay(1000); 
  }
  esp_now_set_self_role(ESP_NOW_ROLE_CONTROLLER);
  esp_now_register_send_cb(OnDataSent);
  esp_now_add_peer(receiverAddress, ESP_NOW_ROLE_SLAVE, 1, NULL, 0);
}

void loop() {
  strcpy(myData.nachricht, "Ich bin der ESP8266 Sender");
  byte result = esp_now_send(receiverAddress, (uint8_t *) &myData, sizeof(myData));
  if (result != 0) {
    Serial.println("\n Sending error");
  } 
  delay(1000);
}