Use the Vonage Messages API's vonage.messages.send() method. Provide the recipient's number, your Vonage virtual number, and the message text in the request body. Ensure your Vonage application is set up correctly with the necessary credentials and linked virtual number as described in the guide's setup steps.

The Vonage Messages API is a unified API for sending and receiving messages across various channels, including SMS. It offers comprehensive features for sending SMS programmatically, receiving inbound SMS to your virtual number, and tracking message delivery status through webhooks.

Using Application ID and Private Key with the Vonage Messages API enhances security by using JWT (JSON Web Tokens) for authentication. This approach is preferred over sending API Key/Secret with each request, as it reduces the risk of credential exposure.

Set up a webhook endpoint in your Node.js/Express application (e.g., /webhooks/inbound) and configure this URL in your Vonage Application settings. Vonage will send an HTTP POST request to this endpoint whenever an SMS is sent to your linked virtual number.

Run ngrok http <your-port> (e.g., ngrok http 3000) in a separate terminal. Copy the HTTPS forwarding URL provided by ngrok. Update your .env file's BASE_WEBHOOK_URL with this URL and configure your Vonage Application's inbound and status URLs using this base URL.

JWT verification ensures that incoming webhook requests genuinely originate from Vonage, preventing unauthorized access or malicious actors from spoofing webhook events. It is crucial for production security.

Configure a status webhook URL (e.g., /webhooks/status) in your Vonage application settings. Vonage will send POST requests to this endpoint with real-time delivery status updates (e.g., 'submitted', 'delivered', 'failed') for each message sent via the Messages API.

You'll need a Vonage API account, API Key and Secret, a purchased Vonage virtual number, Node.js and npm installed, ngrok for development, and a basic understanding of Node.js, Express, and APIs. The guide details how to acquire and configure each of these elements.

Implement JWT verification for all webhook endpoints to ensure requests are from Vonage. Regularly check and update your private key. Refer to Vonage's official documentation for the most accurate and up-to-date security recommendations.

The Messages API is Vonage's recommended approach for modern SMS integrations. It offers a unified API for various channels, including SMS, provides JWT-based webhook security, and has webhooks for inbound messages and delivery statuses. The SMS API is being superseded by the Messages API. For new projects, always use the Messages API.

The guide recommends E.164 format for phone numbers (e.g., +14155552671). While the Messages API may accept other formats, using E.164 promotes consistency and avoids potential issues.

Use try...catch blocks around API calls and within webhook handlers. Log detailed error information from err.response.data when available. Return appropriate HTTP status codes to indicate errors, distinguishing between bad user input (4xx errors) and server-side or Vonage issues (5xx errors).