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Network Connectivity Troubleshooting Guide

Error Analysis

Error: No route to host (OS Error: No route to host, errno = 113)
Target: 10.83.12.71:5000

This means the mobile device cannot establish a connection to the backend server.

Step 1: Verify Backend Server IP Address

Your backend is currently configured to listen on 0.0.0.0:5000 (all network interfaces).

Check Your Current IP Address:

Windows:

ipconfig

Look for your WiFi adapter's IPv4 address. Common patterns:

  • 192.168.x.x (Home WiFi)
  • 10.x.x.x (Some networks)
  • 172.16.x.x to 172.31.x.x (Private networks)

Current configured IP in mobile app: 10.83.12.71

Step 2: Verify Backend is Running and Accessible

A. Check if backend is listening on port 5000:

netstat -an | findstr :5000

You should see:

TCP    0.0.0.0:5000           0.0.0.0:0              LISTENING

B. Test from your PC browser:

http://localhost:5000/health
http://<YOUR_IP>:5000/health

Both should return: {"status":"OK","environment":"development"}

Step 3: Test Network Connectivity

From Your PC:

Option 1: Using curl (if installed)

curl http://10.83.12.71:5000/health

Option 2: Using PowerShell

Invoke-WebRequest -Uri "http://10.83.12.71:5000/health"

If these fail, your PC's IP has changed!

Step 4: Fix the Issue

Scenario A: IP Address Changed ✅ MOST LIKELY

Your WiFi IP address has changed from 10.83.12.71 to something else.

Solution:

  1. Run ipconfig and note your current WiFi IPv4 address
  2. Update mobile app: 
    // File: mobile_app/lib/services/api_service.dart (line 11)
final String baseUrl = 'http://YOUR_NEW_IP:5000';
  3. Rebuild: flutter build apk
  4. Install: flutter install --device-id=10BE5820BZ0009L

Scenario B: Firewall Blocking Connection

Windows Firewall might be blocking incoming connections.

Solution:

# Run PowerShell as Administrator
netsh advfirewall firewall add rule name="Flask Server" dir=in action=allow protocol=TCP localport=5000

Or use Windows Firewall GUI:

  1. Open Windows Defender Firewall
  2. Click "Advanced settings"
  3. Click "Inbound Rules" → "New Rule"
  4. Port → TCP → 5000 → Allow the connection
  5. Name it "SafeCopy Backend"

Scenario C: Mobile and PC on Different Networks

Check:

  • PC connected to WiFi: YOUR_WIFI_NAME
  • Mobile connected to WiFi: SAME_WIFI_NAME ← Must match!

Solution:

  • Connect both devices to the same WiFi network
  • Disable mobile data on your phone
  • Some WiFi routers have "AP Isolation" - disable it in router settings

Step 5: Alternative - Use USB Debugging (Temporary)

If network issues persist, use ADB port forwarding:

# Forward mobile port 5000 to PC port 5000
adb -s 10BE5820BZ0009L reverse tcp:5000 tcp:5000

Then in mobile app:

final String baseUrl = 'http://localhost:5000';

This makes the app connect through USB instead of WiFi.

Quick Fix Commands

1. Find your current IP:

ipconfig | findstr IPv4

2. Test backend connectivity:

curl http://localhost:5000/health
curl http://YOUR_IP:5000/health

3. Check if port 5000 is listening:

netstat -an | findstr :5000

4. Add firewall rule:

netsh advfirewall firewall add rule name="SafeCopy_Backend" dir=in action=allow protocol=TCP localport=5000

5. Test from mobile (using ADB):

adb -s 10BE5820BZ0009L shell curl http://YOUR_IP:5000/health

Common Issues Checklist

  • Backend server is running (python app.py)
  • Server shows "Server running on http://0.0.0.0:5000"
  • Both devices on same WiFi network
  • Mobile data disabled on phone
  • Firewall allows port 5000
  • IP address in mobile app matches current PC IP
  • Can access http://YOUR_IP:5000/health from PC browser

Expected Log Output (When Working)

Backend console should show:

Server running on http://0.0.0.0:5000
Flask server started on port 5000

Mobile app should show:

Upload details:
   Owner ID: surya@gmail.com
   File name: environment_final_report_vf.pdf
   Base URL: http://10.83.12.71:5000
✅ Public key retrieved successfully
✅ Symmetric key encrypted
📤 Uploading file...
✅ File uploaded successfully

NOT:

❌ Upload error: Get public key error: ClientException with SocketException: No route to host