*
 * <p>Here is a simple example of how to use a {@code ServiceManager} to start a server.
 *
 * <pre>{@code
 * class Server {
 *   public static void main(String[] args) {
 *     Set<Service> services = ...;
 *     ServiceManager manager = new ServiceManager(services);
 *     manager.addListener(new Listener() {
 *         public void stopped() {}