Multiplayer Distributed Game

Question

Hi,
I have written a 2 player distributed TicTacToe game and am having some problems converting it into a multiplayer game. I have tried countless methods to do this, unfortunately to no avail. I have attached the server code with the hopes that someone might have experience with this and will be able to give me a hand. Also, sorry for the length of this post but I thought it would be easier to supply the entire server code so you could see what I am trying to accomplish. Thanks.
import java.net.*;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.util.*;
public class TicTacToeServer extends JFrame {
     static protected Set activePlayers = new HashSet();
     static final int DEFAULT_PORT = 5000;
     private JTextArea output;
     private JScrollPane scrollPane;
     private Board board;
     public TicTacToeServer(String args[]) {
          super("Tic Tac Toe Server");
          output = new JTextArea();
          scrollPane = new JScrollPane(output);
          getContentPane().add(scrollPane, BorderLayout.CENTER);
          setSize(300,300);
          setVisible(true);
          int port = DEFAULT_PORT;
          if (args.length > 0) {
               try {
                    port = Integer.parseInt(args[0]);
               catch(NumberFormatException e) {
                    display(e.toString());
          board = new Board(this);
          try {
               ServerSocket server = new ServerSocket(port);
               Socket connection;
               while (true) {
                    display("Waiting for players to connect...");
                    connection = server.accept();
                    ClientResponseHandler newPlayer = new ClientResponseHandler(connection, board, this);
                    activePlayers.add(newPlayer);
                    newPlayer.start();
          catch(Exception e) {
               display(e.toString());
     public void display(String s) {
          output.append(s + "\n");
     public static void main(String args[]) {
          new TicTacToeServer(args);
class ClientResponseHandler extends Thread {
     private Socket connection;
       private BufferedReader in;
       private PrintWriter out;
       private Board board;   
       private int playerNumber;
     private TicTacToeServer server;
     public ClientResponseHandler(Socket connection, Board board, TicTacToeServer server) {
          this.connection = connection;
          this.board = board;
          this.server = server;
         server.display("A player has connected");
          try {
               in  = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                out = new PrintWriter(connection.getOutputStream(), true);
          catch(Exception e) {
               server.display(e.toString());
     public synchronized void sendChatMessage(String msg) {
          if (out != null) {
               out.println("Chat" + msg);
               out.flush();
     public void run()  {
          playerNumber = board.addPlayer(out);
          if (playerNumber != -1)
               parsePlayerInput();
          else    
               out.println("Player limit reached");
          closeLink();
     private void parsePlayerInput() {
          String inputFromPlayer;
          boolean done = false;
          try {
               while (!done) {
                    if((inputFromPlayer = in.readLine()) == null)
                         done = true;
                    else {
                         server.display("Client --> Server: " + inputFromPlayer);
                          if (inputFromPlayer.startsWith("Socket is closed"))
                              done = true;
                         else if (inputFromPlayer.startsWith("Chat")) {
                              Iterator iter = server.activePlayers.iterator();
                              while (iter.hasNext()) {
                                   ClientResponseHandler t = (ClientResponseHandler) iter.next();
                                   if (t != this)
                                        t.sendChatMessage(inputFromPlayer.substring(4));
                         else
                              parsePlayerCellLocation(inputFromPlayer);
          catch(IOException e) {
               server.display(e.toString());
     private void parsePlayerCellLocation(String inputFromPlayer) {
               if (inputFromPlayer.startsWith("Client clicked cell ")) {
                    try {
                         int clientCellLocation = Integer.parseInt(inputFromPlayer.substring(20,21).trim());
                         board.tryMove(playerNumber, clientCellLocation);
                    catch(NumberFormatException e) {
                         server.display(e.toString());
     private void closeLink() {
          try {
               board.delPlayer(playerNumber);
                connection.close();
                server.display("Client connection closed by player " + playerNumber + "\n");
         catch(Exception e) {
               server.display(e.toString());
class Board {
     private int board[];
     private Player player[];
     private int numPlayers;
       private boolean gameEnabled, isGameOver;
     private int currentPlayerNumber;
     private TicTacToeServer server;
     public Board(TicTacToeServer server) {
          this.server = server;
          board = new int[9];
         initializeBoard();
          player = new Player[2];
             player[0] = new Player("X");
         player[1] = new Player("O");
          numPlayers = 0;
         gameEnabled = false;
         isGameOver = false;
     private void initializeBoard() {
          for(int i = 0; i < 9; i++)
               board[i] = -1;
     synchronized public int addPlayer(PrintWriter out) {
          if (numPlayers == 2)  
               return -1;          
          player[numPlayers].setOutput(out);
          String token = player[numPlayers].getToken();
          server.display("Server --> Client: Player connected " + token);
          player[numPlayers].sendMessage("Player connected " + token);
          numPlayers++;
          if (numPlayers == 2) {  
               gameEnabled = true;
               currentPlayerNumber = 0;
               player[currentPlayerNumber].sendMessage("Game is ready to begin");  
          return numPlayers - 1;
     synchronized public void delPlayer(int playerNumber) {
          player[playerNumber].disable();
          if (numPlayers == 2) {
               int otherId = (playerNumber + 1) % 2;
               player[otherId].sendMessage("Player exited");
                player[otherId].disable();
          numPlayers = 0;
         gameEnabled = false;
             isGameOver = false;
         initializeBoard();
     synchronized public void tryMove(int playerNumber, int cellNumber) {
          if (!gameEnabled)                
               player[playerNumber].sendMessage("Only 1 player connected");
          else if (isGameOver)
               player[playerNumber].sendMessage("Game over");
         else if (currentPlayerNumber != playerNumber)    
                player[playerNumber].sendMessage("Not your turn");
         else if (cellOccupied(cellNumber))       
                player[playerNumber].sendMessage("Cell occupied");
         else {       
                board[cellNumber] = playerNumber;
               player[playerNumber].sendMessage("Valid move " + cellNumber);
                currentPlayerNumber = (currentPlayerNumber + 1) % 2;  
                player[currentPlayerNumber].sendMessage("Update opp " + cellNumber);
               if (gameOver()) {
                    player[playerNumber].sendMessage("Player won");   
                  player[currentPlayerNumber].sendMessage("Player lost"); 
                  isGameOver = true;
     private boolean cellOccupied(int cellNumber) {
          return (board[cellNumber] != -1);
     private boolean gameOver() {
          if (sameVals(0,1,2) || sameVals(3,4,5) || sameVals(6,7,8) ||
               sameVals(0,3,6) || sameVals(1,4,7) || sameVals(2,5,8) ||
               sameVals(0,4,8) || sameVals(6,4,2))
               return true;
               return false;
     private boolean sameVals(int c1, int c2, int c3) {
          if ((board[c1] == board[c2]) && (board[c2] == board[c3]) && (board[c1] != -1))
               return true;
          return false;
class Player {
     String token;
     PrintWriter out;
     public Player(String token) {
          this.token = token;
         out = null;
     public void setOutput(PrintWriter out) {
          this.out = out;
     public String getToken() {
          return token;
     public void disable() {
          out = null;
     public void sendMessage(String msg) {
          out.println(msg);
}

Answer 1

I suggest you seperate you network handling logic from your game code.
Then debug the message sent and received.
BTW: And use a code formatter.
I have a simple example chat program here.
http://www.jtoolkit.org/space/Point+to+Point.html