Multiple client chat server

[Rob Brew]

Hi all.

i'm trying to write a chat server which can handle multiple clients, i've looked online and can't figure out how to name my threads, i thought:

int i = 0;
Thread t[i] = new Thread(inr);
t[i++].start();

would do it but this won't compile. Also realised i get a JVM bind error when the second client connects, if i don't pass the socket to the thread what do i pass?

Thanks in advance.

Rob.

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package argosserver;

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author Rob
 */
public class ArgosServer {

    
    Socket clientSocket = null;
       
    ArgosServer(Socket s) {
        this.clientSocket = s;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
       try {
           int i = 0;
           while (true) { 
           ServerSocket serverSock = new ServerSocket(4242);
            Socket clientSocket = serverSock.accept();
            IncomingReader inr = new IncomingReader(clientSocket);
            Thread t = new Thread(inr);
            t.start();
                    
           }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        

    }
}

    

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package argosserver;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

/**
 *
 * @author Rob
 */
public class IncomingReader implements Runnable {
    BufferedReader in = null;
    PrintWriter writer = null;
    Socket clientSocket = null;
    public IncomingReader (Socket clientSocket) {
    
    this.clientSocket = clientSocket;
    }
        public void run() {



            try {
            PrintWriter writer = new PrintWriter(clientSocket.getOutputStream());

            InputStreamReader isr = new InputStreamReader(clientSocket.getInputStream());
            in = new BufferedReader(isr);

                String message = "";
                System.out.println("server  in run");

                while ((message = in.readLine()) != null) {
                    if (message.equals("marco")) {
                        writer.write("polo\n");
                        writer.flush();
                        System.out.println("read marco");

                    }
                }
            } catch (Exception ex) {
                ex.printStackTrace();
            }

        }
    }

[Wouter Oet]

You need to create 1 ServerSocket which then creates multiple Sockets.

[Paul Clapham]

I don't know what you're talking about when you say "name my threads". Threads don't need names. Let me point you to Oracle's tutorial about client-server socket handling, that might help more.

Writing the Server Side of a Socket

[Rob Brew]

Thanks for your replies.

Paul i start a new thread, t, which passes the sockets to class incomingreader. But when the loop goes round i can't start a new thread t as it's already defined. So how do i have t1, t2, t3 etc as different threads spawned from main?

[Wouter Oet]

Something like

List<Thread> threads = new ArrayList<Thread>();
while(something) {
   Thread t = new Thread(new SomeRunnable());
   t.start();
   threads.add(t);
}

[Rob Brew]

When i do the following multiple clients can connect and work.:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package argosserver;

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author Rob
 */
public class ArgosServer {

    Socket clientSocket = null;

    ArgosServer(Socket s) {
        this.clientSocket = s;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        List<Thread> threads = new ArrayList<Thread>();
        try {
            int i = 0;
            while (true) {
                ServerSocket serverSock = new ServerSocket(4242);
                Socket clientSocket1 = serverSock.accept();
                IncomingReader inr = new IncomingReader(clientSocket1);
                Thread t = new Thread(inr);
                t.start();
                threads.add(t);
            Socket clientSocket2 = serverSock.accept();
                IncomingReader inr1 = new IncomingReader(clientSocket2);
                Thread t1 = new Thread(inr1);
                t1.start();
                threads.add(t1);
                    
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }



    }
}

When i do:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package argosserver;

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author Rob
 */
public class ArgosServer {

    Socket clientSocket = null;

    ArgosServer(Socket s) {
        this.clientSocket = s;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        List<Thread> threads = new ArrayList<Thread>();
        try {
            int i = 0;
            while (true) {
                ServerSocket serverSock = new ServerSocket(4242);
                Socket clientSocket1 = serverSock.accept();
                IncomingReader inr = new IncomingReader(clientSocket1);
                Thread t = new Thread(inr);
                t.start();
                threads.add(t);
           }
        } catch (Exception ex) {
            ex.printStackTrace();
        }



    }
}

the second client crashes with the error message:

java.net.SocketException: Connection reset

.

I need to use different names for Thread t, such as t1 t2 etc. How do i do this?

[fred rosenberger]

you cannot have dynamic variable names in java.

[Rob Brew]

so how would i go about creating multiple threads whenever i get a Server.accept? i don't want to change the name of a variable, merely to give each thread a different name. I've seen other code, such as below from simlple chat server /client use:
name[integer counter] as the name, but this won't work for me. No idea why not.

[Paul Clapham]

I don't know why you are getting hung up on "names" for threads. You create a thread like this:

new Thread(runnable)

Is there some feature of your application which needs to keep track of the threads you create?

[Rob Brew]

When i use:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package argosserver;

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author Rob
 */
public class ArgosServer {

    Socket clientSocket = null;
    int i = 0;
    static List<Thread> threads = new ArrayList<Thread>();

    ArgosServer(Socket s) {
        this.clientSocket = s;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        
        try {
            while (true) {
                ServerSocket serverSock = new ServerSocket(4242);
                Socket clientSocket1 = serverSock.accept();
                
                Thread t = new Thread(new IncomingReader(clientSocket1));
                t.start();
            }   
        } catch (Exception ex) {
            ex.printStackTrace();
        }



    }
}

i get

java.net.SocketException: Connection reset

.

When i implement the same code again in the same loop (as in the earlier post) multiple clients can connect without problem. I was thinking it was because t was using the same name but now i'm not sure.

[Rob Brew]

Problem solved, ServerSocket was in the while loop, not outside of it