Can not connect Android with Win10 proxy

[Jaro]

I'm trying to set up environment where I can display HTTP/HTTPS traffic coming from/to the android device on my Windows 10 machine. I followed this manual for Fiddler Everywhere https://docs.telerik.com/fiddler-everywhere/traffic/configure-android However I can't seem to be able to access the Proxy from my phone.

Root certificate has been installed/trusted.

I enabled the proxy in "Settings"

Live Traffic is enabled and shows all requests for that Win10 machine.

IP address of the wireless interface of the Windows device is 192.168.8.110

I'm using Samsung S21 with Android 13.
I then set up this IP and 8866 port as proxy for my WiFi connection on the Android phone and navigated to ipv4.fiddler:8866 But it constantly responds with ERR_TIMED_OUT and keeps reloading. Also nothing from the mobile device is visible in Fiddler Live Traffic on Windows machine. I wasn't able to find a related topic on the forum. Any help would be greatly appreciated.

[Nick Iliev]

Hello Jaro Maro,

 

The inability to open the Fiddler echo address (http://ipv4.fiddler:8866) after the proxy address is set on your WiFi shows that, for some reason, your mobile device cannot reach the Fidder Everywhere host machine. Different reasons can cause that:

- The first thing to check and verify is that both the Fiddler Everywhere host machine and the mobile device are using the same WiFi network. In case the host machine uses multiple network adapters, try to deactivate the other adapted and leave only the WiFI adapter (that you will use with your Android device).

- Ensure that the Fiddler Everywhere host runs on the specified address (192.168.8.110),

- Verify that your Android device can be seen from the Fiddler Everywhere host. You can ping the mobile device through its local IP address (see the IP from Samsunsg's Settings > About device> Status menu). You can open a terminal on your Fiddler Everywhere host and type

ping 192.168.8.21

Where 192.168.8.21 is an example IP to substitute with your actual Android IP address from the connected WiFi network. You should see a successful reply if you can reach the Android device from the Fiddler host machine. Otherwise, you will see the destination unreachable or request timeout (or another error message), indicating that your WiFi network is limited (by your router, by a security policy, network administrators, etc.). In that case, the best action is to contact your network administrators for further instructions.

- Restart Fiddler Everywhere, reset its certificates (Settings > HTTPS > Advanced > Reset Certificates), and ensure that the option Allow Remote Computers to Connect is still active (as in the provided screenshot).

- Toggle the Live Traffic switch to Capturing mode (as in the provided screenshot)

- Close the mobile Android browser, and re-enter the manual proxy settings for the WiFi connection.

- Re-open the mobile browser and try to load the Fiddler Everywhere echo address http://ipv4.fiddler:8866 or any other HTTP address like http://example.com. If you can open the latter (http://example.com) but not the echo address, then you can use the proxy, but probably a local limitation is preventing you from reaching out to the echo address. You can workaround this by manually exporting the Fiddler certificate (through Fiddler Everywhere > Settings > HTTPS > Advanced > Export Root Certificate (Der/Binary format)) and sending it through the external source to your Android device. Then open, install, and trust the certificate to be able to capture & decrypt HTTPS traffic

If you are still not able to open any HTTP address (both the echo address and http://example.com fails), switch the used WiFi network (again for both Fiddler Everywhere host and for the Android device) with a network that does not apply security policies or restricts the usage of proxies and ports.

 

Regards,
Nick Iliev
Progress Telerik

[Jaro]

Thanks for coming back!

To simplify the network I switched computers to one with just 2 network interfaces and connected Android device with a WIndows 10 host directly. Basically shared the ethernet internet connection via WiFi. So the router and other network equipment should be out of the question. The two devices, Win10 host and Android device, are communicating directly with each other.

At this point I can ping Android device from Win10 host. I can access shared internet connection from Android device. All good so far. I can't see any HTTP requests coming from Android device in Fiddler interface.

I now set up the manual proxy on Android device to 192.168.137.1 (Win 10 WiFi adapter) and port 8866 as configured in Fiddler Everywhere. I'm still able to ping Android device from Win10 host, but on Android I can't connect to http://example.com nor http://ipv4.fiddler:8866. 

I tried with all your suggestions,
-regenerated root certificate on Win10, restarted Fiddler,
-Switched OFF "Allow remote computers to Connect", restarted Fiddler
-switched ON "Allow remote computers to Connect", restarted Fiddler
-toggled "Live traffic" switch off and on
-restarted browser on Android (Chrome, Samsung default browser and Kiwi)

Nothing's changed unfortunately. Request is pending for 8 seconds in browser and throws "ERR_TIMED_OUT" Is there anything specific in Windows or Android for that matter that might block this connection? I can't seem to find anything...

Here's a high-tec screenshot of ipconfig and ping

[Nick Iliev]

From the ipconfig screenshot and the previous screenshots (where the proxy is set to 192.168.8.110), I am noticing two issues:

- The first is that the IP of the FIddler host entered on the Android device (192.168.8.110) is not the same as the IP shown in the ipconfig screenshot (192.168.8.111). There is a difference in the last digit (0 vs. 1).

- The second possible issue is that you have two different subnets. While the Fiddler Everywhere host machine operates under 192.168.8.110 with subnet mask 255.255.255.0, the WiFi address of the Android device is from a different subnet (IP 192.168.137.11 / mask 255.255.255.0). Ensure that both of your devices operate under the same subnet so that the proxying can occur.

[Jaro]

There are two subnets since I shared wired connection to this Windows desktop via WiFi adapter. That's expected, with that I wanted to avoid any issues with networking gear.

I downloaded "PingTools" on my Android device and was able to check for open ports with it's help. Turns out 8866 wasn't open for the 192.168.137.1. I had to manually create an inbound rule in Windows Firewall and allow for connections via 8866. That solved it right away :)

Might be worth mentioning this somewhere, or maybe add the inbound rule to Window Firewall automatically? I've had this happen on two separate Windows Computers.

[Nick Iliev]

Thank you for sharing the details of your solution with us! Indeed, opening port 8866 (or whatever port Fiddler is set to use) for the remote device is a must - we will add this as a note in our documentation articles for configuring remote devices and devices situated on different networks.