How can we build a chatting app like whatsapp that works on phone text messaging

To build a chat app like WhatsApp that runs on phone text messaging, you need to use an SMS Gateway API, set up a backend server, and create a mobile user interface. [1, 2]

Core Architecture & Tools

SMS Gateway API: Use services like Twilio or Vonage to send and receive real phone text messages (SMS) programmatically.
Backend Server: Build a server using Node.js or Erlang to process incoming and outgoing text logs.
Database: Store user phone numbers, message history, and profile data using databases like PostgreSQL, Firebase Firestore, or MongoDB.
Mobile Frontend: Develop cross-platform mobile screens using Flutter or React Native so the app works on both Android and iOS. [1, 2, 3, 4, 5]

Development Steps

User Verification: Implement phone number login by sending a random verification code via SMS.
Sync Contacts: Request permission to read the phone’s address book and match numbers registered in your database.
Message Routing: Connect your mobile app to the backend so that when a user hits send, the app triggers an API request to dispatch an SMS or sync through your server data pipeline