Adding a Thread Pool to a Server

      while (true) {
        try {
          Socket s = ss.accept();
          ThreadedEchoServer tes = new ThreadedEchoServer(s);
          tes.start();
        }
        catch (IOException e) {
        }

An alternative approach is to create a pool of threads when the server launches, store incoming connections in a queue, and have the threads in the pool progressively remove connections from the queue and process them. This is particularly simple since the operating system does in fact store the incoming connections in a queue. The main change you need to make to implement this is to call accept() in the run() method rather than in the main() method. The program below demonstrates.

import java.net.*;
import java.io.*;


public class PoolEchoServer extends Thread {

  public final static int defaultPort = 2347;
  ServerSocket theServer;
  static int numberOfThreads = 10;
  
  
  public static void main(String[] args) {
  
    int port = defaultPort;
    
    try {
      port = Integer.parseInt(args[0]);
    }
    catch (Exception e) {
    }
    if (port <= 0 || port >= 65536) port = defaultPort;
    
    try {
      ServerSocket ss = new ServerSocket(port);
      for (int i = 0; i < numberOfThreads; i++) {
        PoolEchoServer pes = new PoolEchoServer(ss); 
        pes.start();
      }
    }
    catch (IOException e) {
      System.err.println(e);
    }

  }
  
  public PoolEchoServer(ServerSocket ss) {
    theServer = ss;
  }
  
  public void run() {
  
    while (true) {
      try {
        Socket s = theServer.accept();
        OutputStream out = s.getOutputStream();
        InputStream in = s.getInputStream();
        while (true) {
          int n = in.read();
          if (n == -1) break;
          out.write(n);
          out.flush();
        } // end while
      } // end try
      catch (IOException e) {
      }       
    } // end while
    
  } // end run
    
}