package ora.ch6;import java.io.InterruptedIOException;import javax.microedition.io.Connector;import javax.microedition.io.Datagram;import javax.microedition.io.DatagramConnection;import javax.microedition.lcdui.Alert;import javax.microedition.lcdui.AlertType;import javax.microedition.lcdui.Command;import javax.microedition.lcdui.CommandListener;import javax.microedition.lcdui.Display;import javax.microedition.lcdui.Displayable;import javax.microedition.lcdui.Form;import javax.microedition.lcdui.StringItem;import javax.microedition.lcdui.TextField;import javax.microedition.midlet.MIDlet;import javax.microedition.midlet.MIDletStateChangeException;public class TimeMIDlet extends MIDlet                    implements CommandListener, Runnable {    private Display display;    private Form addressForm;    private Form connectForm;    private Form displayForm;    private Command backCommand;    private Command exitCommand;    private Command okCommand;    private StringItem messageLabel;    private TextField serverName;    protected void startApp() throws MIDletStateChangeException {        if (display == null) {            initialize();            display.setCurrent(addressForm);        }    }    protected void pauseApp() {    }    protected void destroyApp(boolean unconditional)                        throws MIDletStateChangeException {    }    public void commandAction(Command cmd, Displayable d) {        if (cmd == okCommand) {            Thread t = new Thread(this);            t.start();        } else if (cmd == backCommand) {            display.setCurrent(addressForm);        } else if (cmd == exitCommand) {            try {                destroyApp(true);            } catch (MIDletStateChangeException ex) {            }            notifyDestroyed();        }    }    public void run() {        DatagramConnection conn = null;        display.setCurrent(connectForm);        try {            // Build the name string for the Connector open method            String server = serverName.getString();            String name = "datagram://" + server + ":" + 13;            conn = (DatagramConnection)Connector.open(name,                                    Connector.READ_WRITE, false);            // Build and send an empty datagram            Datagram dg = conn.newDatagram(10);            dg.setData("Hello".getBytes(), 0, 5);            conn.send(dg);            // Receive the reply            Datagram rdg = conn.newDatagram(512);            conn.receive(rdg);            messageLabel.setText(new String(rdg.getData(), 0, rdg.getLength()));            display.setCurrent(displayForm);        } catch (InterruptedIOException iex) {            display.callSerially(new Runnable() {                public void run() {                    Alert alert = new Alert("No Reply",                        "No reply was received.\n" +                        "Please check the server address and try again.", null,                        AlertType.ERROR);                    alert.setTimeout(Alert.FOREVER);                    display.setCurrent(alert, addressForm);                }            });            return;        } catch (Exception ex) {            display.callSerially(new Runnable() {                public void run() {                    Alert alert = new Alert("Invalid Address",                        "The supplied address is invalid\n" +                        "Please correct it and try again.", null,                        AlertType.ERROR);                    alert.setTimeout(Alert.FOREVER);                    display.setCurrent(alert, addressForm);                }            });            return;        } catch (Error err) {            System.out.println(err);            err.printStackTrace();        }    }    private void initialize() {        display = Display.getDisplay(this);        // Commands        exitCommand = new Command("Exit", Command.EXIT, 0);        okCommand = new Command("OK", Command.OK, 0);        backCommand = new Command("Back", Command.BACK, 0);        // The address form        addressForm = new Form("Network Time");        serverName = new TextField("Time Server name:", "tock.usno.navy.mil",                                            256, TextField.ANY);        addressForm.append(serverName);        addressForm.addCommand(okCommand);        addressForm.addCommand(exitCommand);        addressForm.setCommandListener(this);        // The connect form        connectForm = new Form("Sending");        messageLabel = new StringItem(null,                    "Sending the datagram...\nPlease wait.");        connectForm.append(messageLabel);        connectForm.addCommand(backCommand);        connectForm.setCommandListener(this);        // The display form        displayForm = new Form("Server Reply");        messageLabel = new StringItem(null, null);        displayForm.append(messageLabel);        displayForm.addCommand(backCommand);        displayForm.setCommandListener(this);    }}