node_modules/pac-resolver/myIpAddress.js

/**
 * Module dependencies.
 */

var net = require('net');
var ip = require('ip');

/**
 * Module exports.
 */

module.exports = myIpAddress;

myIpAddress.async = true;

/**
 * Returns the IP address of the host that the Navigator is running on, as
 * a string in the dot-separated integer format.
 *
 * Example:
 *
 * ``` js
 * myIpAddress()
 *   // would return the string "198.95.249.79" if you were running the
 *   // Navigator on that host.
 * ```
 *
 * @return {String} external IP address
 */

function myIpAddress (fn) {
  // 8.8.8.8:53 is "Google Public DNS":
  // https://developers.google.com/speed/public-dns/
  var socket = net.connect({ host: '8.8.8.8', port: 53 });
  socket.once('error', function(err) {
    // if we fail to access Google DNS (as in firewall blocks access), 
    // fallback to querying IP locally
    fn(null, ip.address());
  });
  socket.once('connect', function () {
    socket.removeListener('error', fn);
    var ip = socket.address().address;
    socket.destroy();
    fn(null, ip);
  });
}