#define p1 2
#define p2 3

void setup() {
  Serial.begin(9600);
  pinMode(p1, OUTPUT);
  pinMode(p2, OUTPUT);
  Serial.println("ARDUINO : CONNECTED");
}

void loop() {
  if (Serial.available()) {
    String state = Serial.readString();
    //Serial.println(state);   // For debug
    state.toUpperCase();
    int msgLgt = state.length();
    //Serial.println(msgLgt); // For debug
    int semiC = state.indexOf(";");
    String firstArg = state.substring(0, semiC);
    //Serial.println(firstArg);   // For debug
    String ScndArg = state.substring(semiC + 1, msgLgt-1);
    ///Serial.println(ScndArg);   // For debug

    if (firstArg == "LED1ON") {
      digitalWrite(p1, HIGH);
    }
    if (firstArg == "LED1OFF") {
      digitalWrite(p1, LOW);
    }
    if (ScndArg == "LED2ON") {
      digitalWrite(p2, HIGH);
    }
    if (ScndArg == "LED2OFF") {
      digitalWrite(p2, LOW);
    }
    // ... and next condition LED
  }
}