void setup() {
  Serial.begin(9600);
  int isSharp=-1;
  int isAtSign=-1;
  String msg="@QUX1!@CSUX1#&C,0,0,0,0!";
  isAtSign = msg.indexOf("@CSUX1#");
      if (isAtSign != -1) isSharp = msg.indexOf('#', isAtSign);
      if ( isSharp != -1) {
        if (msg.length() > 17) {
          Serial.println("ok");
        }
       
      }
}

void loop() {
  // put your main code here, to run repeatedly:

}