Example -- Drive iRobot Create for 1 Second and Stop in Java

DriveCreate.java

import java.io.IOException;
import java.io.OutputStream;

import gnu.io.CommPort;
import gnu.io.CommPortIdentifier;
import gnu.io.NoSuchPortException;
import gnu.io.PortInUseException;
import gnu.io.SerialPort;
import gnu.io.UnsupportedCommOperationException;

class DriveCreate {
	public static void main(String args[]) {
		try {
			// Boilerplate stuff from RXTX example code.
			CommPortIdentifier portIdentifier = CommPortIdentifier.getPortIdentifier("/dev/rfcomm0");
			CommPort commPort = portIdentifier.open("RDIS", 2000);
			SerialPort serialPort = (SerialPort) commPort;
			serialPort.setSerialPortParams(57600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
			OutputStream out = serialPort.getOutputStream();
			
			// Create Primitives as byte arrays
			byte startup[] = { (byte) 128 };
			byte full[] = { (byte) 132 };
			byte goForward[] = { (byte) 137, (byte) 0, (byte) 200, (byte) 0x80, (byte) 0x00 };
			byte stop[] = { (byte) 137, (byte) 0, (byte) 0, (byte) 0, (byte) 0 };
			
			// Send the bytes.
			out.write(startup);
			Thread.sleep(1000);
			out.write(full);
			Thread.sleep(1000);
			out.write(goForward);
			Thread.sleep(1000);
			out.write(stop);
			
			// Cleanup
			serialPort.close();
		} catch (NoSuchPortException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (PortInUseException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (UnsupportedCommOperationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

A note: RXTX will "discover" serial ports that look like "/dev/ttyS_", and our "/dev/rfcomm_" does not look like that so it thinks it's not a serial port. Therefore, you have to tell it explicitly that it is a serial port by running it like this:

java -Dgnu.io.rxtx.SerialPorts=/dev/rfcomm0 MyClass

Explained here: http://mailman.qbang.org/pipermail/rxtx/2008-July/9480809.html