CONNECTION_TROUBLESHOOTING.md

🔧 Connection Troubleshooting Guide

❌ Problem: "Connection refused" Error

If you're seeing this error in the Flutter app:

Login error: ClientException with SocketException: Connection refused (OS Error: Connection refused, errno = 111), address = localhost, port = 8000

This means the Flutter app cannot connect to the backend server. Here are the solutions:

✅ Solutions

1. Make Sure Backend is Running

Start the backend server:

cd /Users/modder/evmaster-workshop/backend
source venv/bin/activate
python main.py

Verify it's running:

curl http://localhost:8000/health
# Should return: {"status":"healthy"}

2. Platform-Specific URLs

The app now automatically detects your platform and uses the correct URL:

Platform	URL Used
Android Emulator	http://10.0.2.2:8000
iOS Simulator	http://localhost:8000
Physical Device	Need your computer's IP

3. For Physical Devices

If testing on a real phone/tablet, you need your computer's IP address:

Find your computer's IP:

# On macOS/Linux:
ifconfig | grep "inet " | grep -v 127.0.0.1

# On Windows:
ipconfig | findstr "IPv4"

Update the config: Edit /Users/modder/evmaster-workshop/client/lib/config/api_config.dart and replace YOUR_COMPUTER_IP with your actual IP address.

4. Alternative: Use Your IP Address

If the automatic detection doesn't work, manually set your computer's IP:

1. Find your IP address (e.g., 192.168.1.100)
2. Edit lib/config/api_config.dart:

static String get baseUrl {
  if (kDebugMode) {
    return 'http://192.168.1.100:8000'; // Use your IP
  } else {
    return 'https://your-api-domain.com';
  }
}

5. Check Firewall Settings

Make sure your firewall allows connections on port 8000:

macOS:

sudo pfctl -f /etc/pf.conf

Check if port is blocked:

netstat -an | grep 8000

6. Alternative Port

If port 8000 is blocked, use a different port:

Backend (main.py):

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8080)  # Use port 8080

Flutter (api_config.dart):

return 'http://10.0.2.2:8080';  // Update port

🔍 Debugging Steps

1. Check Backend Status

curl http://localhost:8000/health
curl http://localhost:8000/docs  # API documentation

2. Test Login Endpoint

curl -X POST http://localhost:8000/auth/login \
  -H "Content-Type: application/json" \
  -d '{"client_code":"DEMO123"}'

3. Check Current Configuration

The login screen now shows debug info:

• Current API URL being used
• Platform (Android/iOS)
• Suggested demo codes

4. Network Connectivity

Make sure your device/emulator has internet access:

# From device/emulator, try:
ping google.com

🚀 Quick Fix Commands

Option 1: Restart Everything

# Terminal 1: Backend
cd backend && source venv/bin/activate && python main.py

# Terminal 2: Flutter  
cd client && flutter clean && flutter run

Option 2: Use Different Device

# List available devices
flutter devices

# Run on specific device
flutter run -d <device-id>

Option 3: Test API Manually

# Test backend is working
curl http://localhost:8000/health

# Test login endpoint
curl -X POST http://localhost:8000/auth/login \
  -H "Content-Type: application/json" \
  -d '{"client_code":"TEST123"}'

✅ Success Indicators

You'll know it's working when:

1. ✅ curl http://localhost:8000/health returns {"status":"healthy"}
2. ✅ Login screen shows correct API URL in debug info
3. ✅ No "Connection refused" errors in Flutter logs
4. ✅ Login with "DEMO123" successfully enters the app

📱 Platform Notes

Android Emulator

• ✅ Uses http://10.0.2.2:8000 automatically
• ✅ Should work out of the box

iOS Simulator

• ✅ Uses http://localhost:8000 automatically
• ✅ Should work out of the box

Physical Devices

• ⚠️ Requires your computer's IP address
• ⚠️ Device and computer must be on same WiFi network
• ⚠️ Firewall must allow connections on port 8000

🆘 Still Having Issues?

1. Check the Flutter logs for specific error messages
2. Verify backend logs show incoming requests
3. Try different devices (emulator vs physical)
4. Check network connectivity between device and computer
5. Restart both backend and Flutter app

The connection should work seamlessly once the backend is running and the correct URL is configured! 🚗✨