Così:
codice:
class Server extends Thread {

   private class ServerThread extends Thread {
      ...
      public ServerThread(Socket s) {
         ...
      }
   }

   private Vector mieiClients;

   public Server() {
      ...
      mieiClients = new Vector();
      ...
   }

   public void run() {
      ...
      Socket s = serverSocket.accept();
      mieiClients.add( new ServerThread(s) );
      ((ServerThread) mieiClients.elementAt(mieiClients.size()-1)).start();
   }
}
Ciao.