anchor.diff:     */
     static const String PORT_OPTION = "port";
   
  +  /**
  +   * The name of the option used to specify the log file.
  +   */
  +  static const String LOG_FILE_OPTION = "log";
  +
     SocketServer socketServer = new SocketServer();
   
     HttpAnalysisServer httpServer;
  
positive.code: import 'package:analysis_server/src/socket_server.dart';
  import 'package:analysis_server/stdio_server.dart';
  import 'package:args/args.dart';
  
  /**
   * The [Driver] class represents a single running instance of the analysis
  
negative.code:         negatable: false);
      parser.addOption(PORT_OPTION, help:
          "[port] the port on which the server will listen");
      parser.addOption(LOG_FILE_OPTION, help:
          "[path] file to log debugging messages to");
  
      ArgResults results = parser.parse(args);
      if (results[HELP_OPTION]) {
        _printUsage(parser);
        return;
      }
      if (results[LOG_FILE_OPTION] != null) {
        try {
          File file = new File(results[LOG_FILE_OPTION]);
          IOSink sink = file.openWrite();
          Logger.root.onRecord.listen((LogRecord record) {
            sink.writeln(record);
          });
        } catch (exception) {
          print('Could not open log file: $exception');
          exitCode = 1;
          return;
        }
      }
      int port;
      bool serve_http = false;
  