int Relay =4;  

void setup() {
 
  Serial.begin(9600);
  Serial.println("Hello, ESP32!");
  pinMode(Relay, OUTPUT);
}

void loop() {
  digitalWrite(Relay, HIGH);
  if(digitalRead(Relay)==1){ Serial.println("ON");}
  delay(500); 
  digitalWrite(Relay, LOW);  
  if(digitalRead(Relay)==0){ Serial.println("OFF");}
  delay(500);
}