Use Vonage's Messages API and webhooks. Set up a webhook endpoint in your application to receive real-time status updates like 'submitted,' 'delivered,' or 'failed' from Vonage after sending an SMS message via their API.

It's an API that lets you send and receive messages, including SMS, and track their delivery status. You integrate it into your application using the Vonage Node.js SDK or other language-specific libraries. It's more robust than 'fire and forget' methods.

Webhooks provide real-time delivery updates pushed directly to your application. This is more efficient than constantly polling the API and lets you react immediately to changes in message status, building more reliable systems.

Whenever your application needs to send SMS messages reliably and track their delivery status in real time. It's especially important for time-sensitive communications and two-factor authentication.

Use Express.js to create a server and the Vonage Node.js SDK to interact with the Messages API. You'll also need environment variables for your API credentials and webhook URLs. Ngrok helps during development.

A unique identifier for your application within the Vonage platform. It's required for using the Messages API. You create an application in the Vonage Dashboard and note its ID for configuration.

Ngrok creates a public, secure tunnel to your local development server, allowing Vonage to send webhooks to your machine during testing. This is necessary because local servers aren't publicly accessible on the internet.

It guarantees the integrity and authenticity of the webhook requests. By using a shared secret, you confirm requests genuinely originated from Vonage and haven't been tampered with. This is crucial for security.

Use the 'jsonwebtoken' library and the Vonage Signature Secret from your application dashboard. Importantly, use the raw request body, not the parsed JSON, when verifying the signature against the token from the 'Authorization' header.

Typical statuses include 'submitted' (sent to Vonage), 'delivered' (reached handset), 'failed,' 'rejected' (by the carrier), 'accepted' (intermediate carrier status), and 'undeliverable.' Not all statuses are guaranteed due to carrier limitations.

Wrap your webhook handler logic in 'try...catch' blocks to handle errors gracefully. Always acknowledge receipt with a 200 OK response, even if your internal processing fails, to prevent Vonage retries. Log errors thoroughly using a structured logger.

Check server and ngrok logs, verify the webhook URL in your Vonage application settings matches your server's URL, and check for firewall issues. Inspect the Vonage API logs for errors reported by Vonage while trying to reach your webhook.

Vonage uses the raw, unaltered request body to generate the JWT signature, not the parsed JSON. Therefore, you must capture the raw body using middleware like body-parser before any JSON parsing occurs to ensure accurate signature verification.

Use the + sign followed by the country code and phone number without any spaces or special characters. Example: +14155550101. Validate user-provided numbers strictly to avoid errors.