Use the Vonage Messages API and Node.js SDK. The `sendSmsMessage` function handles sending SMS messages via the API, specifying the recipient's number, your Vonage number, and the message content. Ensure your Vonage number is linked to your application in the Vonage dashboard.

Set up webhooks to receive incoming WhatsApp messages. Configure the inbound webhook URL in your Vonage application settings and WhatsApp Sandbox settings, pointing to your public ngrok URL (during development) or your deployed application URL, appended with '/webhooks/inbound'. Your server must respond with a 200 OK status to acknowledge receipt.

The Vonage Messages API is a unified interface for sending and receiving messages across multiple channels, including SMS, MMS, WhatsApp, Facebook Messenger, and Viber. It simplifies the process of integrating messaging into your applications.

Vonage uses webhooks to deliver incoming messages to your application in real-time. When a message is sent to your Vonage number or WhatsApp Sandbox number, Vonage sends an HTTP POST request to a pre-configured URL on your server, allowing your application to process the message immediately.

Use the WhatsApp Sandbox for testing your WhatsApp integration during development. It allows you to send and receive messages with allowlisted numbers without incurring charges. Remember that for production, you need a Vonage-approved WhatsApp Business Account linked to a verified WhatsApp Business Profile.

Not in the WhatsApp Sandbox. You must allowlist the recipient's WhatsApp number in the Vonage dashboard for testing. In production, users will need to initiate the conversation with you or opt-in to messaging from your business, or you'll need approved pre-registered message templates.

You need a Vonage API account, Node.js (version 18 or higher recommended), ngrok for local development, a personal WhatsApp account, and a purchased Vonage phone number for sending/receiving SMS.

Use the `@vonage/jwt` library, specifically the `verifySignature` function. This function verifies the JWT signature included in incoming webhook requests, ensuring they are authentic and originated from Vonage.

The Vonage Application ID uniquely identifies your application's configuration within the Vonage platform. It connects your code to your Vonage account and its associated numbers, webhooks, and other settings.

The '/webhooks/inbound' route in your Node.js server handles incoming SMS messages. Parse the 'channel', 'message_type', 'from', 'to', and 'text' properties from the request body (`req.body`) to access the sender, content, and other details. Then add your specific business logic to process the message data.

Secure your webhooks by verifying the signature of incoming requests. This requires setting a 'Signature Secret' in your Vonage settings, and using a middleware function in your Node.js app to validate the signature, ensuring the webhook request actually originated from Vonage.

Create a .env file in your project's root directory and add your Vonage API credentials, application details, and other sensitive information. Use the dotenv library to load these variables into your Node.js application during development. For deployment, set these as environment variables on your hosting platform.

The status webhook delivers information about message delivery status and any errors encountered. Log error details like 'code' and 'reason' using structured logging for better analysis. Implement appropriate error handling, including retries or notifications based on specific error codes.

Use ngrok to create a publicly accessible URL for your local server. Configure your Vonage webhooks to point to this ngrok URL. Then test sending messages using curl or Postman to your local server endpoint, and also send actual SMS and WhatsApp messages to trigger the inbound webhooks. Verify all logs on both server and ngrok.

Choose a hosting provider (Heroku, AWS, Google Cloud, etc.), replace ngrok URLs with your permanent domain, manage environment variables securely on the platform (including setting VONAGE_PRIVATE_KEY_CONTENT if using the updated private key handling), update Vonage webhooks to point to the deployed URL, and establish a CI/CD pipeline for automated deployments.