Question

It’s so bad I got to do a hard reboot (Holding down on the power button) and it doesn’t even give me time to debug, so I’m basically screwed if I don’t get a answer on here. I know it’s server sided (As It happens when I don’t run the client, but also happens if I do).

Here is the Server Code:

package cypri.games.cybatarserver;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Vector;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class CybatarServer extends JFrame implements Runnable{
    String verNum = "0.0.0";
    JScrollPane jsp;
    JTextArea mainText;
    boolean stopServer = false;
    boolean waitForPlayers = true;
    Vector<Player> playersConnected;
    byte playerID = -1;

    public CybatarServer(){
        playersConnected = new Vector<Player>();

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setBounds(100, 100, 400, 100);

        this.setTitle("Cybatar Server " + verNum);

        mainText = new JTextArea(50, 10);
        mainText.setText("Welcome to CybatarServer "+ verNum + "!\n");
        mainText.setEditable(false);

        jsp = new JScrollPane(mainText);
        this.add(jsp);

        this.setVisible(true);
    }

    public static void main(String[] args){
        CybatarServer cyserv = new CybatarServer();
        cyserv.run();
    }

    @Override
    public void run() {

        try { 
            final ServerSocket serverSocket = new ServerSocket(44444);


            while(!stopServer){
                if(waitForPlayers){
                    new Thread(new Runnable() {
                        public void run() {

                            Socket clientSocket = null;
                                try {
                                    clientSocket = serverSocket.accept();
                                } catch (IOException e) {
                                    // TODO Auto-generated catch block
                                    e.printStackTrace();
                                }
                                playerID++;
                                new PlayerThread(playerID, playersConnected, mainText, playerID, clientSocket).start();
                                mainText.append("Player " + playerID + " connected!");

                        }
                    }).start();
                }

                else{
                    for(int i = 0; i < playersConnected.size(); i++){
                        playersConnected.get(i).update();
                    }
                }

                Thread.yield();
            }
        } catch (Exception e) { e.printStackTrace(); }
    }
}

Is there anything in here that could cause my PC to completely freeze up? And if so how do I fix it?

Answer 1

I suspect

while(!stopServer){
   if(waitForPlayers){
       new Thread(new Runnable() {
         ....

is generating and invoking a huge number of threads. That will hit your machine hard in terms of CPU (running those threads) and memory (each thread allocates its own stack space).

I suspect instead you want to accept on incoming connections and only then allocate/start a thread. Note that this still leaves you open to a DOS attack (imagine if an unlimited number of players join) but that may not be a practical issue for you.