Maximum number of socket connections?

Question

Hi there,
I've done a test to check what is the maximum simultanenous socket clients can connect to a socketserver.
The code is as follows:
--------- The Server ------------
import java.net.*;
public class Server {
     public void start() {
          int counter = 0;
          try {
               ServerSocket server = new ServerSocket(9999);
               System.out.println("Server started.");
               while (true) {
                    Socket connection = server.accept();
                    counter++;
                    System.out.println("Client " + counter + " connected.");
     catch (Exception ex) {
     public static void main(String args[]) {
          Server obj = new Server();
          obj.start();
----------- The Client -----------
import java.net.*;
public class Client {
     public static final int NUMBER_OF_CLIENTS = 20; // number of simultaneous connections.
     class ClientThread implements Runnable {
          Thread t;
          int id;
          public ClientThread(int id) {
               t = new Thread(this);
               this.id = id;
               t.start();
          public void run() {
               try {
                    Socket connection = new Socket(InetAddress.getLocalHost(), 9999);
                    System.out.println("Client " + id + " connection OK!");
                    //connection.close();
          catch (Exception ex) {
               System.out.println("Client " + id + " connection Failed!");
     public void start() {
          for (int i = 0; i < NUMBER_OF_CLIENTS; i++)     {
               ClientThread t = new ClientThread(i+1);
     public static void main(String args[]) {
          Client c = new Client();
          c.start();
Test env: Windows XP Sp1
Test results: There is atleast one client which has connection refused.
Questions:
1) Is the situation platform-dependent?
2) Is it possible to configure connection limit on server socket?
Thanks for paying attention.
Trung

Answer 1

Oh, it doesn't work!
Client 1 connection OK!
Client 20 connection OK!
Client 19 connection OK!
Client 18 connection OK!
Client 17 connection OK!
Client 16 connection OK!
Client 11 connection OK!
Client 10 connection OK!
Client 15 connection OK!
Client 14 connection OK!
Client 13 connection OK!
Client 9 connection OK!
Client 8 connection OK!
Client 3 connection OK!
Client 4 connection OK!
Client 5 connection OK!
Client 6 connection Failed!
Client 7 connection Failed!
Client 2 connection OK!
Client 12 connection OK!
I've executed 5 times, the 5th one has showed the
error.I doubt this has anything to do with a 'limit' in the OS.
A box can only process so much at once. That includes establishing connections.
High volume situations are handled by using multiple servers and a front end load balancing router.