String message = "Hello World";


void setup() {

Serial.begin(9600);
Serial.println("");

for(int i = 0; i < 12; i = i + 1) {
  Serial.write(message[i]);
}

}

void loop() {

while(!Serial.available()) {
}

  message = Serial.readStringUntil(10);
  Serial.print(message);

}