Tại sao chạy trên wireless toolkit 2.5.2 oke, nhưng chạy trên điện thoại Nokia S40 lại không báo lỗi cũng chẳng hiện nội dụng recive packet từ server. Các bạn test dùm mình đoạn code này nhé :
import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;
import javax.microedition.io.Connector;
import javax.microedition.io.StreamConnection;
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 socket extends MIDlet implements CommandListener, Runnable {

    private Display display;
    private Form addressForm;
    private Form connectForm;
    private Form displayForm;
    private TextField serverName;
    private TextField serverPort;
    private StringItem messageLabel;
    private StringItem errorLabel;
    private Command okCommand;
    private Command exitCommand;
    private Command backCommand;

    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();
            display.setCurrent(connectForm);
        } else if (cmd == backCommand) {
            display.setCurrent(addressForm);
        } else if (cmd == exitCommand) {
            try {
                destroyApp(true);
            } catch (MIDletStateChangeException ex) {
            }
            notifyDestroyed();
        }
    }

    public void run() {
        InputStream is = null;
        OutputStream os = null;
        StreamConnection socket = null;

        try {
            String server = serverName.getString();
            String port = serverPort.getString();
            String name = "socket://" + server + ":" + port;
            socket = (StreamConnection)Connector.open(name, Connector.READ_WRITE);
        } catch (Exception ex) {
            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;
        }

        try {
            // Send a message to the server
            String request = "YMSG  
‡&        0À€xaydungusÀ€2À€xaydungusÀ€1À€xaydungusÀ€244À€1À€6À€Y=v=1&n=dkbmag3enqdvv&l=n0o3kd6ki/o&p=m2jvvvn012000000&iz=&r=mc&lg=en-US&intl=us&np=1; T=z=CEREMBCEREMB1m0CePQkgfANjYzNAY2TjYzNzVOTzEzMzM1MT&a=QAE&sk=DAAWhqLyyUGTr4&ks=EAA5rfYYJl6396GOU6jEn96AQ--~E&d=c2wBTVRFME13RXhPVEUwTURJNU9EWTBORFF5TmpBMk5nLS0BYQFRQUUBZwFFRDRXVlYyNkdFM0hQWkZGN0lTNFpZUEE0SQF0aXABemxVNm1EAXp6AUNFUkVNQkE3RQ--À€98À€usÀ€";

            os = socket.openOutputStream();
            //t =chr(5);
          /// Header(& TargetUser & "À€14À€" & PmText & "À€97À€1À€", String(4, 0), String(4, Chr(0)), 6)
            os.write(request.getBytes());
            os.close();

            // Read the server's reply, up to a maximum
            // of 128 bytes.
            is = socket.openInputStream();
            final int MAX_LENGTH = 5000;
            byte[] buf = new byte[MAX_LENGTH];
            int total = 0;
            while (total < MAX_LENGTH) {
                int count = is.read(buf, total, MAX_LENGTH - total);
                if (count < 0) {
                    break;
                }
                total += count;
            }
            is.close();
          String reply = new String(buf, 0, total);
          if(reply == null ? "" == null : reply.equals("")){
                        Alert alert = new Alert("I/O Error",
                        "An error occurred while communicating with the server.",
                        null, AlertType.ERROR);
            alert.setTimeout(Alert.FOREVER);
            display.setCurrent(alert, addressForm);
          }
            messageLabel.setText(reply);
          /// messageLabel.setText(buf);
            socket.close();
            display.setCurrent(displayForm);
        } catch (IOException ex) {
            Alert alert = new Alert("I/O Error",
                        "An error occurred while communicating with the server.",
                        null, AlertType.ERROR);
            alert.setTimeout(Alert.FOREVER);
            display.setCurrent(alert, addressForm);
            return;

        } finally {
            // Close open streams and the socket
            try {
                if (is != null) {
                    is.close();
                    is = null;
                }
            } catch (IOException ex1) {
            }
            try {
                if (os != null) {
                    os.close();
                    os = null;
                }
            } catch (IOException ex1) {
            }
            try {
                if (socket != null) {
                    socket.close();
                    socket = null;
                }
            } catch (IOException ex1) {
            }
        }
    }

    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("Socket Client");
        serverName = new TextField("Server name:", "68.180.217.11", 256, TextField.ANY);
        serverPort = new TextField("Server port:", "5050", 8, TextField.NUMERIC);
        addressForm.append(serverName);
        addressForm.append(serverPort);
        addressForm.addCommand(okCommand);
        addressForm.addCommand(exitCommand);
        addressForm.setCommandListener(this);

        // The connect form
        connectForm = new Form("Connecting");
        messageLabel = new StringItem(null, "Connecting...\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);
    }
}