Compatibility problem (or?)

Question

(hey ho, I'm a complete newbie)
I wrote a client-server pair in java (or rather, I more or less copied code from the tutorial). The client is an applet. Now, the client works splendid for me, but (as so often) it doesn't work at all for my friends. They all have java installed, and they can run other (and much more complex) applets, so what could be the problem? I'll just post the code so that you can see for yourselves (and yes, I know it looks horrid, it's just a test; I'm a complete newbie, remember?)
import java.io.*;
import java.net.*;
import java.applet.Applet;
import java.awt.TextField;
import java.awt.TextArea;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class KFClient extends Applet implements ActionListener, Runnable {
     Thread com;
     Socket socket = null;
     PrintWriter out = null;
     BufferedReader in = null;
     String response;
     TextField inputField;
     TextArea displayA;
     public void init() {
          inputField = new TextField(60);
          inputField.addActionListener(this);
          displayA = new TextArea(20, 60);
          displayA.setEditable(false);
          add(inputField);
          add(displayA);
     public void start() {
          if (com == null) {
               com = new Thread(this);
          com.start();
     public void run() {
          try {
               socket = new Socket("x.x.x.x", 4444);
               out = new PrintWriter(socket.getOutputStream(), true);
               in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
               while ((response = in.readLine()) != null) {
                    displayA.appendText(response + "\n");
                    if (response.equals("/quit")) break;
               out.close();
               in.close();
               socket.close();
          } catch (Exception e) {
                        displayA.appendText("ok, something went wrong!");
     public void actionPerformed(ActionEvent e) {
          out.println(inputField.getText());
          inputField.setText(null);
}

Answer 1

Ask your friends to turn on the java console in their browsers.
Then they can see the error messages and report them back to you.