Serial I/O on Arduino + serial I/O on Linux

EchoArduino

//Arduino:
#include <Arduino.h>

#define LF 0x0A
char buffer[11];
int idx = 0;

void setup()
{
  Serial.begin(9600);
  Serial.print("Echo start\r\n");
}

void loop()
{
  if (Serial.available() > 0)
  {
    buffer[idx] = Serial.read();

    if (buffer[idx] == LF || idx >= 9)
    {
      buffer[idx + 1] = 0;
      Serial.print("Received message: ");
      Serial.println(buffer);
      idx = -1;
    }
    idx++;
  }
}

//Linux:
stty -F /dev/ttyUSB0 cs8 9600 ignbrk -brkint -icrnl -imaxbel -opost -onlcr -isig -icanon -iexten -echo -echoe -echok -echoctl -echoke noflsh -ixon -crtscts
tail -f /dev/ttyUSB0
echo "1233333333333333" > /dev/ttyUSB0