Need help with connecting different computers with sockets

Question

I have made my own code for a chatting application. Basically, i created a Server that listens for connections from the client and then creates a thread to deal with it. When ever a client types in a String, it gets printed on all of the other computers. Right now i can get this code to work if the Server and CLients are on the same computer, when i try connecting on other computers it gives me a Server timed out out and it does not Connect. here is my code:
Server:
package talk;
import java.net.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.io.*;
public class Ap_server {
     public static void main(String[] args) throws IOException {
          ServerSocket serverSocket = null;
          ArrayList<Socket> sockets=new ArrayList<Socket>();
          ArrayList<PrintWriter> out=new ArrayList<PrintWriter>();
          ArrayList<BufferedReader> in=new ArrayList<BufferedReader>();
          ArrayList<String> name=new ArrayList<String>();
          ArrayList<AP_Thread> threads=new ArrayList<AP_Thread>();
          try {
               serverSocket = new ServerSocket(4831);
          } catch (IOException e) {
               System.err.println("Could not listen on port: 4831.");
               System.exit(-1);
          int i=0;
          while(true)
               sockets.add(serverSocket.accept());
               in.add(new BufferedReader(
                         new InputStreamReader(
                                   sockets.get(i).getInputStream())));
               PrintWriter pri=new PrintWriter(sockets.get(i).getOutputStream(), true);
               AP_Thread temp =new AP_Thread(out,in.get(i),pri);
               threads.add(temp);
               pri.println("Please type in your name");
               name.add(in.get(i).readLine());
               pri.println("Welcome");
               out.add(pri);
               threads.get(i).setn(name.get(i));
               for(int a=0;a<i;a++)
                    out.get(a).println(name.get(i)+" has joined");
               threads.get(i).start();
               i++;
}Client:
import java.io.*;
import java.net.*;
public class Client {
    public static void main(String[] args) throws IOException {
        Socket kkSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;
        try {
            kkSocket = new Socket("SERVER'S IP ADDRESS", 4831);
            out = new PrintWriter(kkSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Don't know about host.");
            System.exit(1);
        } catch (IOException e) {
             e.printStackTrace();
System.exit(1);
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        String fromServer;
        in_Thread temp= new in_Thread(out,stdIn);
        while ((fromServer = in.readLine()) != null) {
            System.out.println(fromServer);}
        out.close();
        in.close();
        stdIn.close();
        kkSocket.close();
}If anyone has an ideas about how i can change the code to make it work on different computers, please post it. Thanks!

Answer 1

Sure. here is the code for AP_Thread:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
public class AP_Thread extends Thread {
     ArrayList<PrintWriter> out;
     PrintWriter ou;
     BufferedReader In;
     String name;
     public AP_Thread(
               ArrayList<PrintWriter> out,BufferedReader In, PrintWriter ou)
          this.out=out;
          this.ou=ou;
          this.In=In;
     public void setn(String s)
          name=s;
     public void run()
               try
                    while(true)
                    String s;
                    s = In.readLine();
                    if (s == null) {break;}
                    if(s.equals("quit"))
                         out.remove(ou);
                         for(int i=0;i<out.size();i++)
                              out.get(i).println(name+" has left");
                    else if(out.size()>1&&!s.equals(""))
                         for(int i=0;i<out.size();i++)
                              if(!ou.equals(out.get(i)))
                                   out.get(i).println(name+": "+s);
               catch(IOException e){}
}And here is the code for in_Thread
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
public class in_Thread extends Thread
     PrintWriter out;
     BufferedReader stdIn;
     public in_Thread(
               PrintWriter out,BufferedReader stdIn)
          this.out=out;
          this.stdIn=stdIn;
          this.start();
     public void run()
          while(true)
               String fromUser;
               try {
                    fromUser = stdIn.readLine();
                    if (fromUser != null&&!fromUser.equals("")) {
                         out.println(fromUser);
                    if(fromUser.equals("quit"))
                         out.close();
                         stdIn.close();
                         break;
               catch (IOException e) {
                    System.err.println("The connection has been closed");
                    break;
}My guess it that is is an firewall problem because i can get it to work when the client and server on are the same computer.