Timer Server
/*
J2ME in a Nutshell
By Kim Topley
ISBN: 0-596-00253-X
*/
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);
}
}
Related examples in the same category
