eunomia-controller/source/react/server/index.js

const express = require('express');
const logger = require('./logger');
const argv = require('minimist')(process.argv.slice(2));
const setup = require('./middlewares');
const isDev = process.env.NODE_ENV !== 'production';
const ngrok = (isDev && process.env.ENABLE_TUNNEL) || argv.tunnel ? require('ngrok') : false;
const resolve = require('path').resolve;

module.exports = () => {
  const app = express();
  return {
    app: app,
    start: () => {
      setup(app, {
        outputPath: resolve(process.cwd(), 'build'),
        publicPath: '/'
      });

      const customHost = argv.host || process.env.HOST;
      const host = customHost || null;
      const prettyHost = customHost || 'localhost';
      const port = argv.port || process.env.PORT || 3000;

      app.listen(port, host, (err) => {
        if (err)
          return logger.error(err.message);

        if (ngrok) {
          ngrok.connect(port, (innerErr, url) => {
            if (innerErr)
              return logger.error(innerErr);
            logger.appStarted(port, prettyHost, url);
          });
        }
        else
          logger.appStarted(port, prettyHost);
      });
    }
  }
}