Java ile seri port işlemleri için yazılmış bir kütüphane mevcut ilk olarak buradaki RXTXcomm-2.2pre2 dosyadan sisteminize uygun klasör içerisindeki dosyayı işletim sisteminizin ana dizinine atınız (örn. windows için C:\windows\).

Buradaki örnek ile seri port üzerinden gelen verileri okumaya yarayan bir uygulama.

Kaynak kodlar için SerialPortReader

package serialportreader;

import gnu.io.SerialPortEventListener;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent;
import gnu.io.SerialPortEventListener;
import java.util.ArrayList;
import java.util.Enumeration;
import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextArea;
import javax.swing.SwingConstants;

/**
 * @author meSutPiskin
 */
public class UI_Main extends javax.swing.JFrame implements SerialPortEventListener {

    /**
     * @param aComPortName the comPortName to set
     */
    public static void setComPortName(String aComPortName) {
        comPortName = aComPortName;
    }

    String inputLine;
    String[] readArray = new String[100];
    SerialPort serialPort;
    int i = 0;
    private static String comPortName = "COM4";

    public static String getComPortName() {
        return comPortName;
    }
    private static final String PORT_NAMES[] = {getComPortName(),};

    private BufferedReader input;

    private static OutputStream output;

    private static int TIME_OUT = 2000;

    private static int DATA_RATE = 9600;

    public void initialize() {

        System.setProperty("gnu.io.rxtx.SerialPorts", getComPortName());

        CommPortIdentifier portId = null;
        Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();

        while (portEnum.hasMoreElements()) {
            CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
            for (String portName : PORT_NAMES) {
                if (currPortId.getName().equals(portName)) {
                    portId = currPortId;
                    break;
                }
            }
        }
        if (portId == null) {
            
            JOptionPane.showMessageDialog(null," PORTUNA BAĞLI CİHAZ YOK!","HATA",JOptionPane.ERROR_MESSAGE);
            System.out.println("PORTA BAĞLI CİHAZ YOK!");
            return;
        }

        try {
            serialPort = (SerialPort) portId.open(this.getClass().getName(), TIME_OUT);

            serialPort.setSerialPortParams(DATA_RATE, SerialPort.DATABITS_8, SerialPort.STOPBITS_1,
                    SerialPort.PARITY_NONE);

            input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
            output = serialPort.getOutputStream();

            serialPort.addEventListener(this);
            serialPort.notifyOnDataAvailable(true);
        } catch (Exception e) {
            System.err.println(e.toString());
        }
    }

    public synchronized void close() {
        if (serialPort != null) {
            serialPort.removeEventListener();
            serialPort.close();
        }
    }

    @Override
    public synchronized void serialEvent(SerialPortEvent oEvent) {

        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                if (input.ready() == true) {
                    inputLine = input.readLine();

                    System.out.println("OKUNAN VERİ:" + inputLine);
                    JOptionPane.showMessageDialog(null,inputLine,"OKUNAN VERİ",JOptionPane.INFORMATION_MESSAGE);

                } else {
                    System.out.println("VERİ OKUNAMIYOR!");
                      JOptionPane.showMessageDialog(null,inputLine,"VERİ OKUNAMIYOR!",JOptionPane.INFORMATION_MESSAGE);

                }
            } catch (Exception e) {
                System.err.println(e.toString());
            }
        }

    }

    public UI_Main() {
        initComponents();

    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        txtBoundRate = new javax.swing.JTextField();
        txtComPortName = new javax.swing.JTextField();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        btnConnect = new javax.swing.JButton();
        txtTimeOut = new javax.swing.JTextField();
        jLabel3 = new javax.swing.JLabel();
        txtReadData = new java.awt.TextArea();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("SERİ PORT VERİ OKU");
        setResizable(false);
        setType(java.awt.Window.Type.UTILITY);

        txtBoundRate.setText("9600");

        txtComPortName.setText("COM1");

        jLabel1.setText("PORT İSMİ");

        jLabel2.setText("BOUND RATE");

        btnConnect.setText("BAĞLAN");
        btnConnect.setCursor(new java.awt.Cursor(java.awt.Cursor.HAND_CURSOR));
        btnConnect.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnConnectActionPerformed(evt);
            }
        });

        txtTimeOut.setText("2000");

        jLabel3.setText("TIME OUT");

        txtReadData.setMinimumSize(new java.awt.Dimension(20, 80));

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jLabel3)
                    .addComponent(jLabel1)
                    .addComponent(jLabel2)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                        .addComponent(txtComPortName, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 136, Short.MAX_VALUE)
                        .addComponent(txtBoundRate, javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(txtTimeOut, javax.swing.GroupLayout.Alignment.LEADING))
                    .addComponent(btnConnect, javax.swing.GroupLayout.PREFERRED_SIZE, 147, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(txtReadData, javax.swing.GroupLayout.DEFAULT_SIZE, 223, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(txtReadData, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jLabel1)
                        .addGap(5, 5, 5)
                        .addComponent(txtComPortName, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(21, 21, 21)
                        .addComponent(jLabel2)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(txtBoundRate, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(28, 28, 28)
                        .addComponent(jLabel3)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(txtTimeOut, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 73, Short.MAX_VALUE)
                        .addComponent(btnConnect, javax.swing.GroupLayout.PREFERRED_SIZE, 42, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

    private void btnConnectActionPerformed(java.awt.event.ActionEvent evt) {                                           
        setComPortName(txtComPortName.getText());
        DATA_RATE = Integer.parseInt(txtBoundRate.getText());
        TIME_OUT = Integer.parseInt(txtTimeOut.getText());
        btnConnect.setText("TEKRAR BAĞLAN");
        UI_Main main = new UI_Main();

        main.initialize();
        Thread t = new Thread() {
            public void run() {
                try {
                    Thread.sleep(1000000);
                } catch (InterruptedException ie) {
                }
            }
        };
        t.start();

        txtReadData.setText(txtComPortName.getText()+" PORT AÇILDI\n");
        txtReadData.setText(txtReadData.getText() + "Veri Bekleniyor...\n");
        

    }                                          

    public static void main(String args[]) {

        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(UI_Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(UI_Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(UI_Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(UI_Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new UI_Main().setVisible(true);

            }
        });

    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton btnConnect;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JTextField txtBoundRate;
    private javax.swing.JTextField txtComPortName;
    private java.awt.TextArea txtReadData;
    private javax.swing.JTextField txtTimeOut;
    // End of variables declaration                   

}