[Java] Simple multi-threaded ServerSocket implementation.

Server.java

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Server implements Runnable {
    private volatile boolean isStopped;
    private ServerSocket serverSocket;
    private final ExecutorService threadPool = Executors.newCachedThreadPool();

    @Override
    public void run() {
        try {
            serverSocket = new ServerSocket(9000);
            serverSocket.setSoTimeout(0);
        } catch (IOException ex) {
            throw new RuntimeException("Unable to open ServerSocket: " + ex.getMessage());
        }
        
        // Run server socket handler in separate thread so accept doesn't block stop
        Thread serverSocketHandler = new Thread(new Runnable() {
            @Override
            public void run() {
                Socket clientSocket;
                int clientNumber = 1;
                while(!isStopped) {
                    try {
                        System.out.println("Waiting for connections...");
                        clientSocket = serverSocket.accept();
                        threadPool.execute(new ClientHandler(clientSocket, clientNumber++));
                    } catch (IOException ex) {
                        errorLog(ex.getMessage());
                    }
                }
            }
        });
        
        serverSocketHandler.start();        
    }
    
    private class ClientHandler implements Runnable {
        @Override
        public void run() {
            System.out.println("Handling client (" + clientNumber + "): " + socket.toString());
            try {
                socket.close();
            } catch(IOException ex) {
                errorLog(ex.getMessage());
            }
        }
        
        public ClientHandler(Socket socket, int clientNumber) {
            this.socket = socket;
            this.clientNumber = clientNumber;
        }
        
        private final Socket socket;
        private final int clientNumber;
    }

    public synchronized void stop() throws IOException {
        System.out.println("Stopping server...");
        isStopped = true;
        if(serverSocket != null)
            serverSocket.close();
        threadPool.shutdown();
    }

    private void errorLog(String message) {
        System.err.println("ERROR: " + message);
    }
    
}