  handler: function ({log} = {}) {
    if (!this.server.options.pasv_url) {
      return this.reply(502);
    }

    this.connector = new PassiveConnector(this);
    return this.connector.setupServer()
    .then((server) => {
      let address = this.server.options.pasv_url;
      // Allow connecting from local
      if (isLocalIP(this.ip)) {
        address = this.ip;
      }
      const {port} = server.address();
      const host = address.replace(/\./g, ',');
      const portByte1 = port / 256 | 0;
      const portByte2 = port % 256;

      return this.reply(227, `PASV OK (${host},${portByte1},${portByte2})`);
    })
    .catch((err) => {
      log.error(err);
      return this.reply(err.code || 425, err.message);
    });
  },
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.