Frequently Asked Questions
This guide provides a step-by-step process to integrate Sinch's inbound SMS capabilities into your Next.js application. It utilizes NextAuth.js for user authentication and Prisma for database interactions, allowing you to securely receive and process SMS messages sent to a dedicated Sinch number linked to user accounts.
NextAuth.js simplifies the implementation of user authentication in your Next.js application. This is crucial for associating incoming SMS messages with specific authenticated user accounts based on their registered phone numbers.
E.164 format (+15551234567) ensures consistent handling of phone numbers, which is essential for reliably linking inbound SMS messages from Sinch to the corresponding user account. It is a globally recognized standard that enables phone number validation, verification and compatibility across different systems, preventing errors or mismatches caused by regional variations.
The Sinch SDK is optional for this specific guide, which focuses on receiving inbound SMS messages. However, the SDK is required if you extend the functionality to send replies or other outbound communications.
While this guide uses PostgreSQL, you can adapt it to use other databases by adjusting the `DATABASE_URL` and configuring the appropriate Prisma provider in the `schema.prisma` file.
Webhook security is paramount. Generate a strong secret with `openssl rand -base64 32` and configure it in both your `.env` file (`SINCH_WEBHOOK_SECRET`) and the Sinch dashboard for the specific webhook endpoint. This secret will be used to verify the signature of incoming webhook requests, ensuring they originate from Sinch and not malicious actors.
The diagram visually illustrates the flow of requests and data between the user, your Next.js application, the Sinch platform, and the database. It highlights the interactions with NextAuth.js for login requests and Prisma for database access, and showcases how the webhooks are processed via an API route.
Use tools like ngrok or the Vercel CLI to expose your local development server to the internet. This will allow Sinch to send webhooks to your local endpoint during development and testing. Make sure to configure the generated URL from ngrok or Vercel as your webhook URL in Sinch.
You'll need Node.js, access to a PostgreSQL database, a Sinch account with API credentials and a dedicated phone number, and basic understanding of React, TypeScript, and REST APIs.
The application assumes that SMS messages are sent in E.164 format. It looks up the user in the database whose `phoneNumber` field matches the incoming `fromNumber` received in the Sinch webhook payload. Accurate and consistent use of E.164 is critical for correct user identification.
The guide is designed for Next.js version 14 or later, using the App Router.
Prisma is a modern Object-Relational Mapper (ORM) that simplifies database interactions. It provides a type-safe way to access and manipulate data in your PostgreSQL database, including creating, updating, and querying users and message data.
TypeScript adds static typing to your project, which improves code maintainability, developer experience with enhanced autocompletion and error detection, and helps catch errors early in development. It's recommended to leverage TypeScript in any large-scale Next.js application.
User passwords are securely hashed using bcryptjs before being stored in the database. This ensures that even if the database is compromised, the raw passwords remain protected.
This guide doesn't explicitly cover deployment steps, however common platforms for deploying a Next.js app include Vercel, Netlify, AWS Amplify, or Google Cloud Run. In your chosen production environment, ensure your environment variables are correctly set, and database connections configured.
This guide provides a complete walkthrough for building a Next.js application featuring user authentication with NextAuth.js and integrating Sinch to handle inbound SMS messages, enabling basic two-way communication capabilities.
We'll cover everything from initial project setup and authentication implementation to receiving and processing Sinch webhooks, securing your application, and deploying it. By the end, you'll have a functional application where authenticated users can potentially receive SMS messages sent to a dedicated Sinch number, linked to their account via their phone number.
Project Overview and Goals
What We're Building:
A web application built with Next.js (App Router) that:
Problem Solved:
This guide addresses the need for applications to programmatically receive and process SMS messages from users, linking them to authenticated user accounts within a modern web framework like Next.js. It provides a secure and scalable foundation for features like SMS-based notifications, customer support interactions, or verification processes.
Technologies Used:
next-auth@beta
(v5). While powerful, beta versions may contain bugs or breaking changes. For maximum stability in production, consider using the latest stable v4 release or carefully test v5 before deploying.)create-next-app
).System Architecture:
Prerequisites:
openssl
command line tool for generating secrets. (Alternatives for Windows include Git Bash, Windows Subsystem for Linux (WSL), or online generation tools - use trusted tools for security-sensitive secrets).Final Outcome:
A deployed Next.js application where users can register/login. Incoming SMS messages sent to the configured Sinch number will be securely received, verified, associated with the correct user based on their registered phone number (assuming consistent E.164 format), and stored in the database.
1. Setting up the Project
Let's initialize our Next.js project and install the necessary dependencies.
1.1 Initialize Next.js Project
Open your terminal and run:
Follow the prompts, ensuring you enable TypeScript, ESLint, Tailwind CSS, the
src/
directory, and the App Router.1.2 Install Dependencies
next-auth@beta
: Authentication library (See disclaimer above regarding beta status).@next-auth/prisma-adapter
: Prisma adapter for NextAuth.prisma
,@prisma/client
: Prisma ORM and client.pg
: PostgreSQL driver (required by Prisma).bcryptjs
,@types/bcryptjs
: Password hashing library and its types.zod
: Schema validation library.@sinch/sdk-core
: Optional, but may be useful for type definitions or if you extend the application to send replies using the Sinch SDK. Not strictly required for receiving and verifying webhooks as shown in this guide.1.3 Set up Prisma
Initialize Prisma in your project:
This creates a
prisma
directory with aschema.prisma
file and a.env
file at the project root.1.4 Configure Environment Variables
Open the
.env
file created by Prisma (or create one if it doesn't exist) and add the following variables. Do not commit this file to version control.DATABASE_URL
: Your full PostgreSQL connection string.AUTH_SECRET
: Generate a strong secret usingopenssl rand -base64 32
in your terminal. Crucial for NextAuth session security.SINCH_PROJECT_ID
,SINCH_APP_KEY
,SINCH_APP_SECRET
: Obtain these from your Sinch account dashboard. Primarily needed if you plan to send outbound messages via the SDK.SINCH_WEBHOOK_SECRET
: This is a secret you create. It needs to be securely generated (e.g., usingopenssl rand -base64 32
) and then configured in the Sinch dashboard for your webhook endpoint. Sinch will use this secret to sign incoming webhook requests.NEXTAUTH_URL
: The canonical URL of your application. Essential for redirects and callbacks.1.5 Define Database Schema
Open
prisma/schema.prisma
and define your models. We assume phone numbers will be stored and handled in E.164 format (e.g.,+15551234567
) for consistency.password
andphoneNumber
(unique, E.164 format assumed) toUser
.Message
model to store SMS details, linked optionally toUser
.@@index
onMessage.userId
andMessage.fromNumber
for potential query performance improvements, although@unique
on other fields already implies an index.1.6 Apply Database Migrations
Run the following command to sync your schema with the database.
(Note: For production, use
prisma migrate dev
andprisma migrate deploy
for robust migration management).1.7 Project Structure Overview
Your
src
directory should look something like this:2. Implementing Core Functionality (Authentication)
We'll set up NextAuth.js for user registration and login using email, password, and phone number.
2.1 Prisma Client Instance
Create a file to instantiate and export your Prisma client singleton.
2.2 NextAuth Base Configuration (
auth.config.ts
)This file defines basic configurations like custom pages and the authorization callback used by the middleware.
2.3 NextAuth Main Configuration (
auth.ts
)This file includes the provider logic (Credentials), database interactions, and password handling.
2.4 Middleware for Route Protection
Create the middleware file to protect routes based on authentication status using the
authorized
callback defined inauth.config.ts
.2.5 Server Actions for Auth (
actions/auth.ts
)Create Server Actions for handling sign-up and login form submissions.
2.6 UI Components (Login and Sign Up Forms)
Create basic form components. Note: These examples assume you have basic
Button
,Input
, andLabel
components. You can create these yourself or install a library likeshadcn/ui
: