Set up a Node.js/Express backend with the Infobip API. This involves installing necessary libraries like `axios`, `multer`, and `libphonenumber-js`, configuring your `.env` file with Infobip credentials, and creating an API endpoint to handle MMS sending logic. The backend will manage file uploads, validate inputs, and interact with the Infobip MMS API.

The Infobip MMS API is part of Infobip's CPaaS (Communications Platform as a Service) offering. It allows developers to send multimedia messages (text and images) programmatically through their platform. This API requires specific request formatting, including `multipart/form-data` for handling binary media files, and authentication using API keys.

Vite is a modern frontend build tool that offers a significantly faster development experience and optimized build process for frameworks like React and Vue. Its speed and efficiency make it a great choice for building the user interface for sending MMS messages through Infobip.

Phone number validation using `libphonenumber-js` should always be performed on the backend before sending any messages through the Infobip API. This ensures data integrity and avoids unnecessary API calls with invalid recipient numbers. Client-side validation can enhance UX but shouldn't replace server-side checks.

Yes, the provided example uses React, but it's easily adaptable to Vue.js. Vite supports both frameworks, and the backend API remains the same regardless of the frontend framework used. The core concepts and setup remain the same, just the frontend components need adjustment.

Use the `multer` middleware in your Node.js backend to handle `multipart/form-data` requests, which are used for file uploads. `multer.memoryStorage` can be used for testing. The frontend should send the image file as part of the form data to the backend endpoint, matching the field name used by Multer.

Axios is used as the HTTP client for both frontend and backend communication with the Infobip API. It simplifies making HTTP requests and provides control over constructing `multipart/form-data` payloads required by Infobip's MMS endpoint.

The monorepo-like structure, with separate 'client' and 'server' directories, keeps frontend and backend code cleanly separated. This improves code organization, simplifies dependency management, and makes it easier to work on each part of the application independently.

Configure CORS (Cross-Origin Resource Sharing) on your backend using the `cors` middleware. Allow requests *only* from the specific URL of your frontend (e.g., `http://localhost:5173` in development) by specifying the `origin` in the `cors` options.

Environment variables store sensitive data (like API keys) and configuration settings outside of your codebase. This enhances security and makes deployment easier by allowing configuration changes without modifying the code itself. Use a `.env` file locally and a secure system in production.

The request to the Infobip MMS API must be a `multipart/form-data` request. It typically includes a 'head' section with JSON data (sender, recipient, subject, etc.) and a 'media' section containing the image file. Always check the official Infobip documentation for the latest structure.

Log in to your Infobip account portal. Go to the API Key Management section (often under 'Developers' or 'Settings'). Create a new API key or use an existing one, copy its value, and locate your account-specific Base URL, which is usually displayed in the same area.

The Infobip Sender Number is the phone number or alphanumeric sender ID that you have registered and configured within your Infobip account for sending MMS messages. It is a required parameter in the API request and identifies the sender of the message.

Implement robust error handling in both frontend and backend. The backend should catch errors during file upload, validation, and API calls, returning informative messages. The frontend should handle errors from the backend gracefully and display user-friendly error messages.