code: public Map<InetSocketAddress, ServerPort> activePorts() {
          final Server server = this.server;
          if (server != null) {
              return server.activePorts();
          } else {
              return Collections.emptyMap();
          }
      }
docs: Returns the ports of the server.
  
  @return the {@link Map} which contains the pairs of local {@link InetSocketAddress} and
  {@link ServerPort} is the server is started. {@link Optional#empty()} otherwise.