Communication between 2 seeeduino stalker v2.3 using xbee s2

Hi,

I'm working on a project which consists in sharing data between 2 stalker seeeduino v2.3 boards with xbee modules. I've already set up the two xbees with X-CTU ( one as coordinatorAT, one as routerAT, same pan ID, same baudrate). I've also done the necessary address modifications.
I've just written 2 simple codes :

transmitter :

void setup()
{
  Serial.begin(9600);
}

void loop()
{
  Serial.print('8');
  delay(1000);
}

receiver :

float data = 0;
int ledPin = 13;

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

void loop(){
  
  while(Serial.available()){
    
    if(Serial.read() == '8'){
      digitalWrite(ledPin, HIGH);
      delay(500);
      digitalWrite(ledPin, LOW);
      delay(500);
    }
  }

      digitalWrite(ledPin, LOW);
}

which are the same i've seen on several websites and seemed to work but it's still not working.
So my question is just : Is there any more configurations for the boards ? the xbee modules? Is there anything more to do i do not know?

The red led which corresponds to the quality transmission (RSSI) lights when the codes are uploaded so i think the two modules can talk to each other.
I also tried using the two boards with the lipo battery and it still not work...

So have you got any ideas?

Thanks !