int relaypin=2;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(relaypin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  while(Serial.available()==0){
  }
  char cmd=Serial.read();
  if(cmd=='1'){
    digitalWrite(relaypin, HIGH);
  }
  else if(cmd=='0'){
    digitalWrite(relaypin,LOW);
  }
  delay(10); // this speeds up the simulation
}