Get Meteor server URL/IP when serving or testing from localhost

meteorDevHelpers.js

import { Meteor } from 'meteor/meteor';
import os from 'os';

// If this were production env var ROOT_URL would have had a value
let rootUrl = Meteor.absoluteUrl();
if ((Meteor.isDevelopment) && (rootUrl === 'http://localhost:3000/')) {
  rootUrl = _getServerUrlFromOs();
}

function _getServerUrlFromOs() {
  // return this if all else fails
  let url = Meteor.absoluteUrl();
  
  const osInterfaces = os.networkInterfaces();
  const serverPort = process.env.PORT;
  if (osInterfaces.eth0) {
    url = `http://${osInterfaces.eth0[0].address}:${serverPort}/`;
    console.log(`[server isDevelopment] Overriding Meteor.absoluteUrl from eth0 to ${url}`);
  }
  else if (osInterfaces.wlan0) {
    url = `http://${osInterfaces.wlan0[0].address}:${serverPort}/`;
    console.log(`[server isDevelopment] Overriding Meteor.absoluteUrl from wlan0 to ${url}`);
  }
  // works only for the 1st Ethernet or WLAN interface in your system
  return url;
}