SendMessage Issue (How can I solve this issue?)

[jeongcatfish]

Hi

RIGHT TO THE POINT!

SendMessage sometimes don't work.

for ex:
led will turn On when I press "A".
but sometimes led is Off even if I press "A" over 2~4 times.

what's wrong with this? (HELP)
and the arduino tx led blinks whenever I press "A"

void setup() {
  Serial.begin(9600);
  pinMode(13,OUTPUT);
}

void loop() {
if(Serial.read()=='1')
  digitalWrite(13,HIGH);
else if(Serial.read() == '2')
  digitalWrite(13,LOW);
}

unity Code

if (Input.GetKeyDown(KeyCode.A))
        {
            Debug.Log("Sending 1");
            serialController.SendSerialMessage("1");
        }

        if (Input.GetKeyDown(KeyCode.Z))
        {
            Debug.Log("Sending 2");
            serialController.SendSerialMessage("2");
        }

[jeongcatfish]

//SOLVED//

char data; //add
void setup() {
  Serial.begin(9600);
  pinMode(13,OUTPUT);
}

void loop() {
data = Serial.read(); //add
if(data=='1')
  digitalWrite(13,HIGH);
else if(data == '2')
  digitalWrite(13,LOW);
}