Send data to arduino from PC in java over Serial (RXTXlib)

Projects Interfacing w/ Software on the Computer
9

Thank you guys for all your answers :slight_smile: I haven't solved my problem yet as I had another part to develop in my project.
Now, I'm back and I tried to send back the data received by arduino to java to show what it really receives.
I also added a sleep after serial.connect .

public static void main(String[] args) throws IOException, PortInUseException, NoSuchPortException{
        SerialPortHandler serial = new SerialPortHandler();
        serial.connect("COM2");
        OutputStream serialOut = serial.getSerialOutputStream();
        InputStream serialIn=serial.getSerialInputStream();
        try {
			Thread.sleep(200);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
        String s = "1";
        byte[] b=new byte[5];
        for (int i = 0 ; i<10; i++){
                System.out.println("write " +i%2);
        	if(i%2==0)
        		serialOut.write(1);
        	else
        		serialOut.write(0);
        	serialOut.flush();

       		try {
				Thread.sleep(100);
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
        	serialIn.read(b);
        	System.out.print("Reçu ");
        	for (int j = 0; j < b.length; j++) {
				System.out.print(b[j]+ " ");
			}
        	System.out.println();
        	try {
				Thread.sleep(3000);
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}

        }  
        serial.disconnect();
    }

In my arduino code, I changed the control sequence and I used ascii code instead of the char itself :

int byteRead;
int led = 13 ;
void setup() {
      Serial.begin(9600);
      pinMode(led, OUTPUT);     
}
void loop() {
     if (Serial.available()) {
            delay(100);
            while (Serial.available()){
                byteRead = Serial.read();
                switch(byteRead){
                case 49:
                   digitalWrite(led, HIGH);
                   break;
                case 0:
                  digitalWrite(led, LOW);
                   break;
                default:
                  break;
            }  
        Serial.write(byteRead);     
      }
     }
delay(500);
}

That's what I receive in the java console :
write 0
Reçu 0 0 0 0 0
write 1
Reçu 0 0 0 0 0
write 0
Reçu 0 0 0 0 0
write 1
Reçu 0 0 0 0 0
and the led doesn't blink of course.
when I insert the serial.write into the case process :

case 49:
                   digitalWrite(led, HIGH);
                   serial.write(byteRead)
                   break;

the java program shows :
Reçu -32 1 1 1 1
I don't really know what does -32 stand for.