Define Constant Variables

The Vonage Voice API sends back call information to the webhook addresses we provided in the Vonage Voice Application in the API Dashboard. To receive that data we need an externally accessible URL. This tutorial uses ngrok to provide an externally available URL. For more information on setting up ngrok, follow this tutorial.

After initializing the Vonage Ruby SDK client in the server.rb file, add the following two constant variables, making sure to replace the sample ngrok URL in the BASE_URL constant definition with your own: