Programming Forums - online game

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- - online game (http://www.programmingforums.org/showthread.php?t=15630)

I completed the battleship game that i was working on and posted that other thread with the question but now i have another question. I have made it 2 player so the players enter their name and where they want to place the ships and everything but i want to make it so 2 people can play each other over the internet. I have done a simple echo server in java but i am still confused if i have multiple classes and stuff how i make the server so in the places where now i would display to the screen i want to display to the 2 clients. Would i have the server end run the main battleship program and then just change the display methods to display the board and moves to the clients connected instead of to the screen? I am confused on how i could do that? Thanks for any input. If i have to post code i will but its like 8 classes basically in the board class I have a printBoard() method that prints the board out so that would have to print to the clients connected and i would have to print the prompts and wait for the response from the clients on where to place ships and where to try and hit the opponents ship.

ok so i looked at the echo server example and i think here is what i want. I want it to be that all the server does is prompt the user for their name, where to place the ships and then when its their turn what row and column to try and attack the other persons ship. It will take that information into the appropiate methods and take the turn or place the ship so right now i have a method that reads from the command line so that would have to read from a Socket instead right? And then the server would send back that players board back to the appropiate client connected and then send to both players if they hit a ship or missed. I have all the logic correct i just seem to be stuck on sending and recieving from a socket to and from the server.

Ok the more I think about this the more i think that it is simpler then what i am trying to do. Basically if each client has a copy of the battleship program and each connects to the same server then couldn't the server just be used to relay the moves to the other client and that is what would be used as input into the program? So each battleship program would only have 1 player and 1 board and the moves that are made against that player and board come across the server from the second client right?

Yeah, the client and server revision is much simpler and easier. It sounds like a great plan, but I don't understand the last part, "board come across the server from the second client right?" If the only data being transmitted is each player's moves, then there is no need to transmit the board because each client will interpret the received move accordingly. Like you said, the received data would be the other player's move and the each client would distinguish a win or loss.

Sorry, that wording is a little confusing i mean the move would be sent to the server and that move would be done against the player's board. So each client would just get 1 player and 1 board and the move against those boards would be taken from the server. But does that sound like a good plan? I've never done anything like this over the internet before so i dont really know what the best design would be.

so to start i am just trying to make 2 clients and a server. The clients will connect to the server and pass a message from one client to the other and it is not working right. The message never gets sent and the server and both clients just hang. Do i need a different name for the different client Sockets? If so I don't know how i would do this because both people playing will be running exact copies of the same program and connect to the server and then the server passes messages between them.

Here is the server code i have

import java.net.*;
import java.io.*;
 
public class Server
{
    public static void main(String[] args) throws IOException
    {
        ServerSocket srvr = new ServerSocket(1234);
         Socket skt1 = new Socket();
 
         skt1 = srvr.accept();
         System.out.print("Server has connected!\n");
         skt1 = srvr.accept();
         System.out.print("Server has connected!\n");
 
        // network IO for client
        PrintWriter out1 = new PrintWriter(skt1.getOutputStream(), true);
        BufferedReader in1 = new BufferedReader(
                                new InputStreamReader(
                                skt1.getInputStream()));
        String line = null;
        line = in1.readLine();
        out1.println(line);
 
 
        out1.close();
        in1.close(); 
        skt1.close();
    } // end main 
} // end class Server

here is the client code I have

import java.io.*;
import java.net.*;
 
public class Client {
    public static void main(String[] args) throws IOException
    {
       Socket skt1 = new Socket("Carl1", 1234);
       PrintWriter out = new PrintWriter(skt1.getOutputStream(), true);
       BufferedReader in = new BufferedReader(new InputStreamReader(
                                        skt1.getInputStream()));
 
 
    String line = "Send this to the other client";
    while(true)
    {
      try
      {
         line = in.readLine();
         System.out.println(line);
         out.println(line);
       } // end try
      //catches bad user input and throws exception
      catch (NumberFormatException ex)
      {
            System.out.print("Error bad data: ");
      } // end catch
    } // end while
    } // end main
} // end Client

I want the one client to send the String line to the server and then the server to pass it to the second client. This is like how the battleship game will work one player sends the row and column he wants to hit and the server sends that information to the other client.

Alright I have an echo server that can connect to clients and echo back what they enter. Now I am stuck on how do i get the input from one client and send it to another client rather than back to the client it came from. I have 3 classes and i will post them. If someone could let me know what i need to do to make it so instead of the server echoing the information it passes the information to a second client.

Sever, main method

import java.net.*;
import java.io.*;
 
import java.net.*;
 
public class Server
{
 
    public static void main(String[] args) throws java.io.IOException
    {   
        ServerSocket s = new ServerSocket(1234);
 
        while(true)
        {
            System.out.println("Listenning...");
            (new ServerThread(s.accept())).start();
            System.out.println("Spawned Thread.");
        } // end while
    } // end main
} // end Server

ServerThread - created for each new client that connects

import java.net.*;
import java.io.*;
 
public class ServerThread extends Thread
{
    private BufferedReader input = null;
    private PrintWriter output = null;
    private PrintWriter output1 = null;
    private BufferedReader keyInput = null;
 
    /** Creates a new instance of MudServerThread */
    public ServerThread(Socket sock)
    {
        try
        {
            input = new BufferedReader(new InputStreamReader(sock.getInputStream()));
            output = new PrintWriter(sock.getOutputStream(), true);
 
            keyInput = new BufferedReader(new InputStreamReader(System.in));
        } // end try
        catch(IOException e)
        {
            System.err.println("Problem with thread!!");
            System.exit(1);
        } // end catch
    } // end ServerThread
 
    public void run()
    {
       String line = "";
        while (true)
        {
          try
          {
               line = input.readLine();
              System.out.println(line);
              output.println(line);
 
 
         } // end try
         catch(IOException e)
         {
             System.err.println(e);
             System.exit(1);
         } // end catch
        } // end while   
    } // end run
} // end class ServerThread

the Client class

import java.io.*;
import java.net.*;
import java.util.*;
 
public class Client {
    public static void main(String[] args) throws IOException
    {
       Socket skt1 = new Socket("192.168.1.102", 1234);
       PrintWriter out = new PrintWriter(skt1.getOutputStream(), true);
       BufferedReader in = new BufferedReader(new InputStreamReader(
                                        skt1.getInputStream()));
       BufferedReader keyInput = new BufferedReader(new InputStreamReader(System.in));
 
       Random r = new Random();
       int[] ar = new int[10];
 
       for (int i = 0; i < 10; i++)
          ar[i] = r.nextInt(10);
 
    String line = "Send this to the other client";
    while(true)
    {
      try
      {
        // line = in.readLine();
       System.out.println("Enter something");
       out.println(keyInput.readLine());
 
         System.out.println(in.readLine());
         //out.println(line);
         for (int i = 0; i < 10; i++)
             System.out.print(ar[i] + " ");
 
         System.out.println();
 
       } // end try
      //catches bad user input and throws exception
      catch (NumberFormatException ex)
      {
            System.out.print("Error bad data: ");
      } // end catch
    } // end while
    } // end main
} // end Client

I want to help you out. I wrote a program in college which might get you started. I need to go through all the source and make sure that none of it is copyrighted. If it is all written by me (none provided by my professor) then I will send it to you. It is too late to go through it tonight. It seems like you are on the right track so far though.

I would use Socket and ServerSocket for the server class. In the first group of code, your

ServerSocket s = new ServerSocket(1234);

is fine. To make the process easier for me, I globalized the Socket for the class

class Server{
        private Socket connection;
        private ObjectOutputStream output;
        private ObjectInputStream input;

Then in a while loop, have the server connection listening

connection = server.accept();

You also want have, in the loop, a call to a method that establishes the streams and throws IOException

private void streams() throws IOException{
                output=new ObjectOutputStream(connection.getOutputStream());
                output.flush();
                input=new ObjectInputStream(connection.getInputStream());
}

Now, for sending data (I have only done strings) you want to create a method.

private void send(String or_variable){
                try{
                        output.writeObject("String" + or_variable);
                        output.flush();
                }
                catch(IOException ioException){
                }
        }
}

hmm, im not sure about this as i am only just beginning Java so im not sure how it would handle something like what im about to suggest.

When a new client connects to the server a connection is established and sotred. Then it is passed to a new Thread and all data from that client is handled by that thread.

Now if you store that connection in a global array, if this is possible in Java. Then it becomes avaliable to everything. This means that other threads that are running for other clients can access the connection via the global array and send data to it.

Cheers,
Chris