List and connect to a serial port assigned to a bluetooth device on windows with RXTX library

Question

I have to communicate with an arduino via Bluetooth. The arduino is connected to a HC-06 bluetooth module, but this is not the point because I have already checked (with some gurus of Arduino) the bluetooth module and the pairing.

So, as you know, when you pair your pc to a bluetooth device, it could assign to it a couple of COM ports. To communicate via bluetooth you have to "send your messages" through the outgoing port. I wrote a little java program that list the COM ports: the first time I run it, I can see also the outgoing port. By the second time, that COM port will not be showed in the list. Obviously you can't connect to it as well.

Does anyone have an idea of what's happening? This is my (simple) code, very common in many tutorials.

java.util.Enumeration<CommPortIdentifier> portEnum = CommPortIdentifier.getPortIdentifiers();
    while ( portEnum.hasMoreElements() ) 
    {
        CommPortIdentifier portIdentifier = portEnum.nextElement();
        System.out.println(portIdentifier.getName());
    }

I'm stuck and desperate because it doesn't seem to make sense.

Thank you. Michele

lord byron lord byron · Accepted Answer · 2017-01-02T14:14:44

Take a look at this. (Taken from YOUTUBE. The author es Taha Emara) I've made some modifications and it runs fine.

package serial_send;

//import gnu.io.CommPortIdentifier;
import gnu.io.CommPortIdentifier;

/**
 *
 * @author Administrador
 */
public class Test extends javax.swing.JFrame {

    /**
     * Creates new form Test
     */
    public Test() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jButton1 = new javax.swing.JButton();
        jComboBox1 = new javax.swing.JComboBox();
        jTextField1 = new javax.swing.JTextField();
        jButton2 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("puertos disponibles");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "", "", "", "" }));
        jComboBox1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jComboBox1ActionPerformed(evt);
            }
        });

        jButton2.setText("enviar");
        jButton2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton2ActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap(123, Short.MAX_VALUE)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, 194, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 180, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addGap(83, 83, 83))
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                            .addComponent(jTextField1)
                            .addComponent(jButton2, javax.swing.GroupLayout.DEFAULT_SIZE, 152, Short.MAX_VALUE))
                        .addGap(112, 112, 112))))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(29, 29, 29)
                .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 33, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(30, 30, 30)
                .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 57, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(34, 34, 34)
                .addComponent(jButton2)
                .addContainerGap(56, Short.MAX_VALUE))
        );

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

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        java.util.Enumeration<CommPortIdentifier> portEnum = CommPortIdentifier.getPortIdentifiers();
        int i = 0;
        String[] r = new String[25];

        while (portEnum.hasMoreElements() && i < 20) {
            CommPortIdentifier portIdentifier = portEnum.nextElement();

            r[i] = portIdentifier.getName();//+  " - " +  getPortTypeName(portIdentifier.getPortType()) ;

            System.out.println("i= " + i);


            i++;


        }

        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(r));
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        String x = jTextField1.getText();
        Serial sr = new Serial();

        Object selectedItem = jComboBox1.getSelectedItem();

        String com = selectedItem.toString();
        sr.ser(x.getBytes(), com);
        sr.close();


    }                                        

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
    }                                          

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<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 | InstantiationException | IllegalAccessException | javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Test.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Test().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   
}

List and connect to a serial port assigned to a bluetooth device on windows with RXTX library

1 Answers