SMS Relay - Production Ready Mobile App

A secure, efficient SMS relay mobile application that receives SMS requests via Firebase Cloud Messaging and forwards them automatically. Perfect for SMS forwarding services.

Features

✅ One-Time Login - Secure email/password authentication
✅ Firebase Integration - Real-time SMS delivery via FCM (no polling)
✅ SMS Management - Local database tracking of all SMS (sent/failed/pending)
✅ Beautiful UI - Material Design 3 with modern layouts
✅ Offline Support - Works without active internet (buffering capability)
✅ Security - Encrypted authentication tokens, secure API communication
✅ Production Ready - Error handling, logging, crash reporting setup
✅ Zero Polling - Event-driven architecture using Firebase

App Flow

Splash Screen (Check Login)
    ↓
[Logged Out?] → Login Activity → Server Authentication → FCM Token Register
    ↓
[Logged In?] → Dashboard Activity (Main)
    ↓
← Receives SMS via Firebase Cloud Messaging
← Auto-sends SMS to recipient
← Stores record in local database
← Updates server with status

Dashboard Features:
- Welcome message with user email
- Total sent/failed SMS count
- Recent SMS list (3 items)
- View full SMS history button
- Logout button

SMS Status Activity:
- Filter by All/Sent/Failed
- Full SMS history with timestamps
- Message content preview
- Recipient numbers
- Status indicators

Architecture

app/
├── auth/
│   ├── AuthManager.kt          (Authentication logic)
│   └── LoginActivity.kt         (Login UI)
├── core/
│   ├── AppConstants.kt          (Constants)
│   ├── AppUtils.kt              (Utility functions)
│   └── DeviceInfo.kt            (Device information)
├── data/
│   ├── database/
│   │   ├── AppDatabase.kt       (Room database)
│   │   └── SmsDao.kt            (Data access objects)
│   ├── entity/
│   │   └── SmsEntity.kt         (Database entity)
│   ├── model/
│   │   ├── SmsRecord.kt         (Domain model)
│   │   └── User.kt              (User model)
│   └── repository/
│       └── SmsRepository.kt     (Data repository)
├── fcm/
│   ├── FcmManager.kt            (FCM management)
│   └── MyFirebaseService.kt     (FCM message handling)
├── network/
│   ├── ApiClient.kt             (Retrofit setup)
│   ├── ApiService.kt            (API endpoints)
│   └── NetworkManager.kt        (Network operations)
├── sms/
│   ├── SmsManager.kt            (SMS sending logic)
│   └── SmsStatusReceiver.kt     (SMS delivery reports)
├── storage/
│   └── StorageManager.kt        (SharedPreferences wrapper)
├── ui/
│   ├── BaseActivity.kt          (Base activity class)
│   ├── DashboardActivity.kt     (Main dashboard)
│   ├── SmsStatusActivity.kt     (SMS history view)
│   ├── SmsAdapter.kt            (RecyclerView adapter)
│   └── SplashActivity.kt        (Splash screen)
└── SmsRelayApp.kt              (Application class)

res/
├── layout/
│   ├── activity_splash.xml
│   ├── activity_login.xml
│   ├── activity_dashboard.xml
│   ├── activity_sms_status.xml
│   └── item_sms.xml
└── values/
    ├── colors.xml
    ├── dimens.xml
    ├── strings.xml
    └── themes.xml

Setup Instructions

1. Clone and Open in Android Studio

git clone <repository-url>
cd smsrelay
open build.gradle.kts in Android Studio

2. Configure Firebase

1. Go to Firebase Console
2. Create a new project (or select existing)
3. Add Android app with package: site.stackverify.smsrelay
4. Download google-services.json
5. Place it in: app/google-services.json
6. Enable Firebase Cloud Messaging in console

3. Build and Run

# Build the project
./gradlew build

# Run on emulator or device
./gradlew installDebug

4. Server API Integration

Update API endpoints in AppConstants.kt:

const val BASE_URL = "https://your-api.com/api/"

Required API Endpoints:

POST /auth/login

Request:

{
  "email": "user@example.com",
  "password": "password123",
  "appId": "APP_Manufacturer_Model_Timestamp",
  "fcmToken": "FCM_TOKEN_HERE"
}

Response:

{
  "success": true,
  "token": "JWT_TOKEN",
  "message": "Login successful",
  "userId": "USER_ID"
}

POST /device/register-fcm

Request:

{
  "fcmToken": "FCM_TOKEN"
}

Response:

{
  "success": true
}

POST /sms/status

Request:

{
  "smsId": "SMS_ID_FROM_FCM",
  "status": "sent|failed|pending",
  "timestamp": 1234567890
}

Response:

{
  "success": true,
  "message": "Status updated"
}

5. Firebase Cloud Messaging Data Format

Send FCM messages to topic all_devices with this structure:

{
  "data": {
    "action": "send_sms",
    "smsId": "UNIQUE_ID",
    "number": "+1234567890",
    "message": "Hello World"
  }
}

Or for notifications:

{
  "data": {
    "action": "notification",
    "title": "SMS Relay",
    "body": "Message forwarded successfully",
    "id": "NOTIFICATION_ID"
  }
}

Dependencies

• Android Core: AndroidX, Material Design 3
• Networking: Retrofit 2, OkHttp 3, Gson
• Database: Room, Coroutines
• Firebase: Cloud Messaging, Analytics, Crashlytics
• Logging: Timber
• Kotlin: Coroutines, Extensions

Security Features

1. Token-based Authentication - JWT tokens saved securely
2. HTTPS Only - No cleartext traffic in production
3. App Signing - Google Play App Signing enabled
4. ProGuard Obfuscation - Code protection enabled
5. Encrypted Storage - SharedPreferences + EncryptedSharedPreferences
6. Permission Management - Minimal permissions requested
7. Crash Reporting - Firebase Crashlytics integration

Permissions

• SEND_SMS - To send SMS messages
• READ_PHONE_STATE - To detect phone state
• INTERNET - Network communication
• ACCESS_NETWORK_STATE - Network availability check
• WAKE_LOCK - FCM background processing

Logging & Debugging

The app uses Timber for comprehensive logging:

Timber.d("Debug message")
Timber.e(exception, "Error message")
Timber.w("Warning message")

In production build, only errors are logged. Debug logs are suppressed.

Error Handling

The app handles:

• Network failures gracefully
• Invalid credentials
• Missing permissions
• Firebase connection issues
• Database errors
• SMS sending failures

All errors are logged and reported to crash analytics.

Testing

The app is structured for easy unit and integration testing:

• Dependency injection ready
• Repository pattern for data access
• Separate concerns (auth, network, storage, SMS)

Production Checklist

• Update API base URL
• Configure Firebase project
• Download google-services.json
• Set up backend API endpoints
• Enable Firebase Crashlytics
• Configure analytics
• Create signing key for Play Store
• Set up ProGuard/R8
• Test on real devices
• Load test FCM delivery
• Enable backup and restore
• Test offline functionality

Performance Optimization

• Efficient Database Queries - Indexed searches
• Coroutine-based Async - Non-blocking operations
• Lazy Loading - RecyclerView pagination ready
• Memory Management - Proper lifecycle handling
• Network Optimization - Connection pooling, timeout management

Troubleshooting

FCM Messages Not Received

• Check Firebase Cloud Messaging is enabled
• Verify app is subscribed to topic
• Check internet connectivity
• Review logcat for errors

SMS Not Sending

• Verify SMS permission granted
• Check phone has SMS capability
• Verify recipient number format
• Check device has cellular/active SIM

Login Fails

• Verify API endpoint is correct
• Check email/password credentials
• Ensure network connectivity
• Check Firebase token generation

App Crashes

• Check logcat/Crashlytics reports
• Verify all dependencies installed
• Check for null pointer exceptions
• Review error logs in Timber

Version History

• v1.0.0 - Initial production release
  • Complete auth flow
  • SMS handling via FCM
  • SMS history tracking
  • Beautiful Material Design UI
  • Production-ready error handling

License

Proprietary - SMS Relay Service

Support

For support, contact: support@stackverify.site

---

Made with ❤️ for secure SMS relay service