#define BLYNK_TEMPLATE_ID "TMPL3MXj9tM0P"
#define BLYNK_TEMPLATE_NAME "Relay"
#define BLYNK_AUTH_TOKEN "ITSgZ-3oDUGopYpbpng0fgBRRaEKyfSs"

#include <BlynkSimpleEsp32.h>

BlynkTimer timer;

void relayOnOff() {
  int relayState = digitalRead(4);
  digitalWrite(4, !relayState);
  if (relayState == HIGH) {
    Serial.println("Relay OFF");
  } else {
    Serial.println("Relay ON");
  }
}

void setup() {
  pinMode(4, OUTPUT);
  Serial.begin(9600);
  Blynk.begin(BLYNK_AUTH_TOKEN, "Your_WiFi_SSID", "Your_WiFi_Password");
  timer.setInterval(3000L, relayOnOff);
}

void loop() {
  Blynk.run();
  timer.run();
}