code: @Override
      public void start(final Logger logger) {
          try {
              logger.logInfo("Starting OpenDJ server");
              final MemoryBackend backend;
              if (getLdifFile() == null) {
                  backend = new MemoryBackend();
              } else {
                  final InputStream inputStream = new FileInputStream(getLdifFile());
                  final LDIFEntryReader reader = new LDIFEntryReader(inputStream);
                  backend = new MemoryBackend(reader);
              }
              final ServerConnectionFactory<LDAPClientContext, Integer> connectionHandler = Connections.newServerConnectionFactory(backend);
              final LDAPListenerOptions options = new LDAPListenerOptions().setBacklog(4096);
              listener = new LDAPListener("localhost", getServerPort(), connectionHandler, options);
              logger.logInfo("Started OpenDJ server");
          } catch (final IOException e) {
              logger.logError("Error starting OpenDJ server", e);
          }
      }
docs: Start the OpenDJ in-memory directory server.
  
  @param logger Used for logging.