Program: 49759
Project: 49759
Buggy source:
public ChatClient(){
  client=new Client();
  client.start();
  Network.register(client);
  client.addListener(new Listener(){
    public void received(    Connection connection,    Object object){
      if (object instanceof UpdateNames) {
        UpdateNames updateNames=(UpdateNames)object;
        chatFrame.setNames(updateNames.names);
        return;
      }
      if (object instanceof ChatMessage) {
        ChatMessage chatMessage=(ChatMessage)object;
        chatFrame.addMessage(chatMessage.text);
        return;
      }
    }
    public void disconnected(    Connection connection){
      EventQueue.invokeLater(new Runnable(){
        public void run(){
          chatFrame.dispose();
        }
      }
);
    }
  }
);
  String input=(String)JOptionPane.showInputDialog(null,"String_Node_Str","String_Node_Str",JOptionPane.QUESTION_MESSAGE,null,null,"String_Node_Str");
  if (input == null || input.trim().length() == 0)   System.exit(1);
  final String host=input.trim();
  input=(String)JOptionPane.showInputDialog(null,"String_Node_Str","String_Node_Str",JOptionPane.QUESTION_MESSAGE,null,null,"String_Node_Str");
  if (input == null || input.trim().length() == 0)   System.exit(1);
  final String name=input.trim();
  chatFrame=new ChatFrame(host);
  chatFrame.setSendListener(new Runnable(){
    public void run(){
      ChatMessage chatMessage=new ChatMessage();
      chatMessage.text=chatFrame.getSendText();
      client.sendTCP(chatMessage);
    }
  }
);
  chatFrame.setCloseListener(new Runnable(){
    public void run(){
      client.stop();
    }
  }
);
  chatFrame.setVisible(true);
  new Thread("String_Node_Str"){
    public void run(){
      try {
        client.connect(5000,host,Network.port);
      }
 catch (      IOException ex) {
        ex.printStackTrace();
        System.exit(1);
      }
      RegisterName registerName=new RegisterName();
      registerName.name=name;
      client.sendTCP(registerName);
    }
  }
.start();
}

Fixed version (ground truth):
public ChatClient(){
  client=new Client();
  client.start();
  Network.register(client);
  client.addListener(new Listener(){
    public void connected(    Connection connection){
      RegisterName registerName=new RegisterName();
      registerName.name="String_Node_Str";
      client.sendTCP(registerName);
    }
    public void received(    Connection connection,    Object object){
      if (object instanceof UpdateNames) {
        UpdateNames updateNames=(UpdateNames)object;
        chatFrame.setNames(updateNames.names);
        return;
      }
      if (object instanceof ChatMessage) {
        ChatMessage chatMessage=(ChatMessage)object;
        chatFrame.addMessage(chatMessage.text);
        return;
      }
    }
    public void disconnected(    Connection connection){
      EventQueue.invokeLater(new Runnable(){
        public void run(){
          chatFrame.dispose();
        }
      }
);
    }
  }
);
  String input=(String)JOptionPane.showInputDialog(null,"String_Node_Str","String_Node_Str",JOptionPane.QUESTION_MESSAGE,null,null,"String_Node_Str");
  if (input == null || input.trim().length() == 0)   System.exit(1);
  final String host=input.trim();
  input=(String)JOptionPane.showInputDialog(null,"String_Node_Str","String_Node_Str",JOptionPane.QUESTION_MESSAGE,null,null,"String_Node_Str");
  if (input == null || input.trim().length() == 0)   System.exit(1);
  final String name=input.trim();
  chatFrame=new ChatFrame(host);
  chatFrame.setSendListener(new Runnable(){
    public void run(){
      ChatMessage chatMessage=new ChatMessage();
      chatMessage.text=chatFrame.getSendText();
      client.sendTCP(chatMessage);
    }
  }
);
  chatFrame.setCloseListener(new Runnable(){
    public void run(){
      client.stop();
    }
  }
);
  chatFrame.setVisible(true);
  new Thread("String_Node_Str"){
    public void run(){
      try {
        client.connect(5000,host,Network.port);
      }
 catch (      IOException ex) {
        ex.printStackTrace();
        System.exit(1);
      }
    }
  }
.start();
}