I'm trying to communicate between my PC (Windows 7 using Netbeans and RXTX) with an Arduino Pro, using the serial port. The Arduino is actually connected to the PC using an FTDI cable. The code is based on the Java SimpleRead.Java found here. Currently the Arduino simply prints out a string when it starts up. My Java program should print the number of bytes that have been read and then print out the contents. The Java program works, sort of... If the string is long (10 bytes or so) the output will get broken up. So if on the Arduino I print Serial.println("123456789123456789"); //20 bytes including '\r' and '\n' The output of my Java program may look something like: Number of Bytes: 15 1234567891234 Number of Bytes: 5 56789 or Number of Bytes: 12 1234567891 Number of Bytes: 8 23456789 I'm thinking it's a timing problem, because when I manually go through the code using the debugger, the result string is always what it should be: one 20 byte string. I've been messing with various things but I haven't been able to fix the problem. Here is the part of the code that is giving me problems: static int baudrate = 9600, dataBits = SerialPort.DATABITS_8, stopBits = SerialPort.STOPBITS_1, parity = SerialPort.PARITY_NONE; byte[] readBuffer = new byte[128]; ... ... public void serialEvent(SerialPortEvent event) { if (event.getEventType() == SerialPortEvent.DATA_AVAILABLE) { try { if (input.available() > 0) { //Read the InputStream and return the number of bytes read numBytes = input.read(readBuffer); String result = new String(readBuffer,0,numBytes); System.out.println("Number of Bytes: " + numBytes); System.out.println(result); } } catch (IOException e) { System.out.println("Data Available Exception"); } }