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NIM game ... server/client program. Can't get it to work no matter what I do

I need to make a really simple game of Nim in which you connect to a server and play it Not only is the game a Client-Server program, the server class implements runnable (so the game will accept new clients in the server) and the client is a thread as well. I have no idea what isn't workin at all. In the game the server part is supposed to ask the client how many sticks they want to play with, then it will ask how many sticks can we pick up per turn, who should go first (your or me) ... then the real part of the game will start (it will say you move first. how many sticks do you want to take?. And so on.

Here is the program:

/** SERVER **/
import java.io.*;
import java.util.*;
import java.net.*;

public class NimServer2 implements Runnable {

      final static int PORT = 10101;
      private ServerSocket nimListen;
      private int gameSticks, minSticks, maxSticks, sticksLeft, clientSticks, serverSticks;
      private BufferedReader fromClient;
      private PrintWriter toClient;
      private Random rand;
      private boolean gameStarted;
      private Buffer2 buff;

      public NimServer2(){

            buff = new Buffer2();
            rand = new Random();

            gameStarted = false;
            try {
                  nimListen = new ServerSocket(PORT);
            } catch (IOException e){}
            System.out.println("NimServer Started... Waiting for a player...");
      }

      public void run(){
            try {
                  while(true){
                        Socket player = nimListen.accept();
                        System.out.println("\nAccepted a connection from " +
                                    player.getInetAddress().toString());

                        InputStream in = player.getInputStream();
                        OutputStream out = player.getOutputStream();

                        fromClient = new BufferedReader(new InputStreamReader(in));
                        toClient = new PrintWriter(out, true);

                        if(!gameStarted){
                              startNewGame();
                              gameStarted = true;
                              toClient.println("MESSAGE FROM SERVER: Let's Play NIM. Whoever Picks up the last stick wings? \n" + "How many sticks do you want to play with?";
                        } else {
                              serverMove();
                        }
                  }

            } catch(IOException ioe){
                  System.out.println("IO error... in Server");
            }
      }

      private void serverMove(){

            buff.serverMove();
            try {
                  clientSticks = Integer.parseInt(fromClient.readLine());
                  int tmpSticksLeft = sticksLeft - clientSticks;
                  serverSticks = 1 + rand.nextInt(maxSticks);
                  sticksLeft = tmpSticksLeft - serverSticks;
                  toClient.println("SERVER: That leaves " + tmpSticksLeft +
                              " sticks. I pick up " + serverSticks + ". " +
                              sticksLeft + " sticks remain.");
            } catch (NumberFormatException nfe){
            } catch (IOException ioe){}
      }

      private void startNewGame(){
            gameSticks = 31;
            minSticks = 1;
            maxSticks = 4;
            sticksLeft = 0;
            serverSticks = 0;
      }

      public static void main(String[] args){
            NimServer2 ns = new NimServer2();
            Thread nimServ = new Thread(ns);
            nimServ.start();
      }
}

/** CLIENT **/
import java.net.*;
import java.io.*;

public class NimClient implements Runnable {

      final static int PORT = 10101;
      private Socket nimSock;
      private BufferedReader fromServer, userIn;
      private PrintWriter toServer;
      private boolean isDone, gameStarted;
      private Thread nimPlayer;
      private int tempNum = 0;
      private Buffer2 buff;

      public NimClient(String serverIP){

            try{
                  nimSock = new Socket(serverIP, PORT);
                  System.out.println("CLIENT: connected to " + serverIP + ":" + PORT);

                  InputStream input = System.in;
                  InputStream in = nimSock.getInputStream();
                  OutputStream out = nimSock.getOutputStream();

                  userIn = new BufferedReader(new InputStreamReader(input));
                  fromServer = new BufferedReader(new InputStreamReader(in));
                  toServer = new PrintWriter(out, true);
            } catch (UnknownHostException uhe){
                  System.out.println("Cannot connect to host");
                  System.exit(0);
            } catch (IOException ioe){
                  System.out.println("IO error in Client");
                  System.exit(0);
            }

            buff = new Buffer2();
            isDone = false;
            gameStarted = false;

      }

      public void run() {
            while(!isDone){
                  try {
                        if (!gameStarted){
                              System.out.println(fromServer.readLine());
                              gameStarted = true;
                        } else {
                              buff.clientMove();
                              System.out.println(fromServer.readLine());
                              System.out.print("How many sticks do you take?\nINPUT: ");
                              tempNum = Integer.parseInt(userIn.readLine());
                              toServer.println(tempNum);
                        }
                  } catch(NumberFormatException nfe){
                  } catch(IOException ioe){}
            }
      }

      public static void main(String[] args){
            if(args.length != 1){
                  System.out.println("Usage: java NimClient \"HOST IP ADDRESS\"");
                  System.exit(0);
            } else {

                  NimClient nc = new NimClient(args[0]);

                  Thread nimPlayer = new Thread(nc);
                  nimPlayer.start();
            }
      }
}

Thank you for all your help.

lwinkenb

To start with, there is a design error in your server. Right now, you have the Server running on its own thread, instead of having each connection run on a new thread.

The loop that looks like:
while(true){
Socket player = nimListen.accept();

Should not be in the run() method. You could probably put that loop in the main method. Then when a new client connects, you can start a new thread and pass that thread an instance of the socket (player in your example). You might want to consider putting the connection in a new class (call it Connection for instance), and have that class be the one that extends Thread or implement Runnable.

Then you could do this:
while(true) {
Socket player = nimListen.accept();
Connection newConnection = new Connection(player);
newConnection.start();
someDataStructure.add(newConnection); // Have a data structure to hold all the started threads
}

The connection class would look something like:

class Connection extends Thread {
Socket socket;
BufferedReader socketIn;
PrintWriter socketOut;

public Connection(Socket socket) {
this.socket = socket;
//initialize the socketIn and socketOut variables
}

public void run() {
//Start the game here
}
}

lwinkenb

Also you currently have your client running on a seperate thread. This isnt neccessary, your client doesnt need it (unless you're planning on adding some additional functionality later on that will require it. I dont know how the game Nim works to be honest).

As far as I can tell, the client just needs a big while loop:

while(true) {
//read input from the console
//then send data to the server
//then handle the server response
}

Now if the server needs to send data back to the client at random times (not just when the client is listening for a response), then you will need to run a seperate thread to listen for messages from the server. This will depend on the complexity of the game though.