Serial Communication with Palm OS - Part 3/4

package rxtx;

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

import java.io.IOException;
import java.io.InputStream;

public class SerialReader {

    // It's important to set the correct serial port path.
    static final String COMPORT = "/dev/ttyUSB0";
    
    // Also important to set the correct baud rate. Server and Client need the same value.
    static final int BAUD_RATE = 9600;

    /*
     *  This method opens the serial port and calls the read method in order to read from the serial interface.
     */
    public void handlePortInterface() throws Exception {
        
        // The portIdentifier controls the access to communications ports, in this case the serial port.
        CommPortIdentifier portIdentifier = CommPortIdentifier.getPortIdentifier(SerialReader.COMPORT);
        
        // Here is checked if the port is available.
        if (this.checkPort(portIdentifier)) {

            // If the check before was successful, the port gets opened.
            CommPort commPort = portIdentifier.open(this.getClass().getName(), 2000);

            // A small check if the correct kind of port is used.
            if (commPort instanceof SerialPort) {
                SerialPort serialPort = (SerialPort) commPort;
                
                // Now, some parameters, like the baud rate, are set.
                serialPort.setSerialPortParams(SerialReader.BAUD_RATE, SerialPort.DATABITS_8, SerialPort.STOPBITS_1,
                        SerialPort.PARITY_NONE);

                // At this point, the program is ready to read from the serial interface.
                this.readFromSerial(serialPort.getInputStream());

                // After the communication has finished, the port can be closed.
                serialPort.close();

            } else {
                throw new Exception("No serial port!");
            }

        }

    }

    /**
     * This method checks if the serial port is available and not used by another application.
     * 
     * @param portIdentifier
     * @return
     * @throws PortInUseException
     */
    private boolean checkPort(CommPortIdentifier portIdentifier) throws PortInUseException {

        if (portIdentifier.isCurrentlyOwned()) {
            throw new PortInUseException();
        }

        return true;
    }

    /**
     * This function reads from an InputStream and prints the related strings on the console.
     * 
     * @param in
     */
    private void readFromSerial(InputStream in) {
        byte[] buffer = new byte[1024];
        int len = -1;
        try {
            while ((len = in.read(buffer)) > -1) {
                System.out.print(new String(buffer, 0, len));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * The "starting point" of this small program.
     * 
     * @param args
     */
    public static void main(String[] args) {
        try {
            SerialReader sr = new SerialReader();
            sr.handlePortInterface();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}