docs: function start(app) {
      /**
       * Create HTTP server.
       */
  
      const config = require('./config')();
      port = normalizePort(config.get('port'));
      server = http.createServer(app);
  
      /**
       * Listen on provided port, on all network interfaces.
       */
  
      app.set('port', port);
      server.listen(port);
      server.on('error', onError);
      server.on('listening', onListening);
  
      return server;
  }