let paypalProd = 'https://www.sandbox.paypal.com/cgi-bin/webscr';
let paypalSandbox = 'https://www.paypal.com/cgi-bin/webscr';

function validateIPN(data) {
  try {
    let url = (Meteor.settings.paypal.sandbox ? paypalSandbox : paypalProd) +
              '?cmd=_notify-validate';
    return HTTP.post(url, {params: data}) === 'VERIFIED';
  } catch (err) {
    log.error(err);
  }
  return false;
}

Router.route('/paypal/payipn', function payipn() {
  try {
    let data = this.request.body;
    this.response.end('');
    if (validateIPN(data)) {
      log.debug('valid ipn');
      // then do stuffs
    }
  } catch (err) {
    log.error(err);
  }
}, { where: 'server' });