You can send SMS messages with Next.js by creating a Server Action that uses the Vonage SMS API. This action handles form submissions containing the recipient's number and the message content. The Vonage Node.js SDK simplifies the integration with the API within your Next.js environment.

A Delivery Receipt (DLR) is a notification sent by Vonage to your application confirming the delivery status of an SMS message. It provides information about whether the message was successfully delivered, failed, or is still in transit. This allows you to track message delivery and take appropriate action if necessary.

Vonage uses webhooks to asynchronously send data to your application, such as delivery receipts (DLRs) or inbound SMS messages. This eliminates the need for your application to constantly poll Vonage for updates, making the communication process more efficient and real-time.

You can handle inbound SMS messages in Next.js by creating a Route Handler for a specific webhook endpoint (e.g., `/webhook/inbound`). Vonage will send incoming messages to this endpoint, which you can then process within your Next.js application, such as logging the message or routing it to support.

After deploying your Next.js application, go to the Vonage API Dashboard Settings. In the "SMS settings" section, enter your deployed application's URL along with the paths to your webhook endpoints (e.g., `/webhook/status` for DLRs and `/webhook/inbound` for inbound messages). Set the HTTP Method to POST and save the changes.

Zod, a schema declaration and validation library, is beneficial for validating form input on your sending form within a Server Action. This ensures that the data sent to the Vonage SMS API is in the correct format, specifically the E.164 number format for the recipient and an appropriate message length, preventing errors before they reach the API.

You'll need `VONAGE_API_KEY`, `VONAGE_API_SECRET`, and `VONAGE_VIRTUAL_NUMBER`. The API Key and Secret are found in your Vonage Dashboard and are used to authenticate with the Vonage API. The Virtual Number, also found in your Dashboard, is the 'from' number for your SMS messages.

The Next.js App Router is a new routing and data fetching system in Next.js. This example leverages App Router features like Server Actions for form handling and Route Handlers for creating API routes for webhooks, improving the structure and organization of your Next.js project.

Create a Route Handler at `/webhook/status` in your Next.js app. Once your app is deployed and this webhook URL is configured in the Vonage Dashboard, Vonage will send POST requests to this endpoint with delivery status updates for each message you send.

The Vonage Node.js SDK simplifies the process of interacting with the Vonage APIs from within your Node.js environment, which is the server-side environment of your Next.js application. It provides convenient functions for sending SMS messages and other Vonage services.

While you can develop webhook handling logic locally, Vonage webhooks require a publicly accessible URL. Services like ngrok or localtunnel can temporarily expose your local development server to the internet for testing webhook interactions during development, before formally deploying to Vercel.

After completing development, you can deploy the Next.js application to Vercel by connecting your GitHub repository to your Vercel account. Vercel automatically handles the deployment and provides you with a public URL that you can then use to configure your Vonage webhook endpoints.

Vonage provides the ability to sign webhook requests, allowing you to verify their authenticity. This is crucial for security and prevents malicious actors from sending fake data to your webhook endpoints. Use the Vonage Signature Secret with a verification method provided by the SDK or JWT library to achieve this.

The recommended Node.js version is 18.17 or later. Ensure you have this version installed before initializing and developing your Next.js project that integrates with the Vonage SMS API. Node.js is the underlying JavaScript runtime for Next.js server-side functions.