Android URL Blocking: Fix Bi-monthly Issues

TL;DR

Your Android app’s traffic to a specific URL is being blocked every two months. This guide covers common causes and solutions, including checking firewall rules, network configurations, certificate pinning, IP address changes, and potential server-side blocks.

1. Identify the Blocked URL

First, confirm the exact URL that’s consistently being blocked. Note down any error messages your app displays when the block occurs. This information is crucial for troubleshooting.

2. Check Device Firewall & Security Settings

1. Android Firewall: Android doesn’t have a system-wide firewall like Windows or macOS, but some manufacturers (e.g., Huawei, Xiaomi) include their own firewall apps. Check these for rules that might be blocking your app’s network access.
2. Security Apps: Antivirus, mobile security suites, and VPN apps can interfere with network connections. Temporarily disable them to see if the issue resolves. If it does, investigate the app’s settings to allow your app’s traffic.

3. Network Configuration Issues

1. Wi-Fi Router/Network: The problem might be with the Wi-Fi network itself. Try connecting to a different Wi-Fi network (e.g., mobile hotspot) or using cellular data. If it works on another network, the issue is likely with your router’s configuration. Check for MAC address filtering or parental controls that could be blocking access.
2. Proxy Settings: Ensure your Android device isn’t accidentally configured to use a proxy server. Go to Settings > Wi-Fi > Advanced (or Long Press on the network name) > Proxy and verify it’s set to ‘None’.

4. Certificate Pinning Problems

If your app uses certificate pinning, an expired or incorrectly configured pin can cause connection failures that appear as blocking.

1. Check Pin Validity: Verify the validity of the pinned certificates in your app’s code. Expired certificates need to be updated.
2. Pinning Implementation: Review how certificate pinning is implemented. Incorrectly configured pins can block legitimate connections. Consider using a more flexible pinning approach that allows for certificate rotation.

5. IP Address Changes & Server-Side Blocks

The bi-monthly recurrence suggests an external factor, like changes to your server’s or the device’s IP address.

1. Server Logs: Examine your server logs for blocked requests originating from the affected Android devices. Look for patterns related to IP addresses or user agents.
2. Dynamic IP Addresses: If your server uses a dynamic IP address, it might be getting blacklisted periodically by security services. Consider using a static IP address.
3. Rate Limiting: Check if your server has rate limiting enabled that could be triggered after two months of consistent traffic from the same device or IP range.

6. Android System Updates

Rarely, an Android system update can introduce network-related bugs.

1. Check for Updates: Ensure your Android device is running the latest available software updates.
2. Rollback (If Possible): If the issue started after a recent update, consider rolling back to a previous version of Android if possible (this depends on your device manufacturer).

7. App Code Review

Review your app’s networking code for any potential issues.

1. Connection Management: Ensure proper connection handling and error checking. Unclosed connections or unhandled exceptions can lead to unexpected behavior.
2. Network Permissions: Verify that your app has the necessary network permissions declared in its manifest file:

   <uses-permission android_name="android.permission.INTERNET" />

8. Contact Network Provider/Server Administrator

If none of the above steps resolve the issue, contact your network provider or server administrator for assistance. They may be able to identify and fix a problem on their end.