storybook-chromatic/bin/lib/tunnel.js

import localtunnel from '@chromaui/localtunnel';
import setupDebug from 'debug';

import { CHROMATIC_TUNNEL_URL } from '../constants';

const debug = setupDebug('chromatic-cli:tunnel');

export default async function openTunnel({ port, https, host = 'localhost', ...rest }) {
  if (!port) {
    throw new Error('Need to pass a port into `openTunnel`');
  }

  const tunnel = await localtunnel({
    // upstream
    host: CHROMATIC_TUNNEL_URL,
    port,

    // local
    local_host: host, // not a typo
    ...rest,

    // I have no idea, these seem to go unused in the unlaying lib
    https: !!https,
    cert: https && https.cert,
    key: https && https.key,
    ca: https && https.ca,
  });

  tunnel.on('url', url => debug(`Got tunnel url: %s`, url));
  tunnel.on('request', request => debug(`Got request: %O`, request));
  tunnel.tunnelCluster.on('error', error => debug(`Got tunnel cluster error: %O`, error));

  return tunnel;
}