Debugging React Native on Android breaks when using Proxyman

[Justin-Credible]

Description

When using Proxyman as a proxy for an Android device's traffic while running a React Native application in development mode, if React Native debugging is disabled, the app does not work. React will stop with the fatal error Failed to connect to debugger! Timeout while connecting to remote debugger.

When this occurs you can see the websocket traffic in Proxyman: localhost_10-20-2022-15-28-04.proxymanlog.zip

It appears that Proxyman is intercepting the websocket requests which I believe React Native uses for debugging. Something isn't quite working correctly though.

Steps to Reproduce

1. Setup Proxyman as a proxy for an Android emulated or physical device
2. Launch a React Native app in development mode npx react-native start
3. Ensure the Android device has 8081 forwarded to the local dev machine adb reverse tcp:8081 tcp:8081
4. Run the app on the Android emulated/physical device
5. Open the React Native dev menu adb shell input keyevent 82
6. Enable debugging

Current Behavior

Application restarts in debugging mode, but immediately fails with: Failed to connect to debugger! Timeout while connecting to remote debugger.

Expected Behavior

Application restarts in debugging mode and works without any errors.

Environment

• App version: Proxyman 3.11.0 (31100)
• macOS version: macOS Monterey 12.6 (21G115)
• Android version: 12 (via Android emulator), 13 (via Pixel 4a)
• React Native version: 0.63.4

Additional notes

This does not affect iOS when using either the iOS simulator or a physical iOS device. In this case I've noticed that websocket traffic does not show up at all in Proxyman; perhaps this is why iOS doesn't have the same issue?

[NghiaTranUIT]

Thanks for the detailed report @Justin-Credible

This does not affect iOS when using either the iOS simulator or a physical iOS device. In this case I've noticed that websocket traffic does not show up at all in Proxyman; perhaps this is why iOS doesn't have the same issue?

You're right. Websocket on iOS doesn't respect the HTTP Proxy, so it won't go through Proxyman app.

On the other hand, Android does. Maybe it's the reason why your Android app (React Native) doesn't work. I'm going to investigate it now.

Maybe I should bypass all React Native debugging Websocket instead of intercepting it.

[NghiaTranUIT]

Hey @Justin-Credible I've spent hours investigating, but the npx react-native run-android is extremely unreliable 😢

I've followed the official guideline from React Native at https://reactnative.dev/docs/environment-setup

Without opening Proxyman, 9 out of 10, the command just returns an error. I have to remove the emulator and create a new one, it runs successfully Once, then breaks again.

Thus, I could not reliably reproduce the bug. I suppose that it's about the WS via Proxyman when you use adb reverse tcp:8081 tcp:8081 .

If you don't mind, please try to remove all reverse, e.g adb reverse --remove-all, and try again, it might fix the problem.

[Justin-Credible]

Running adb reverse tcp:8081 tcp:8081 is required during development in most cases, as this is how React Native normally loads the application bundle. I tried it without using adb reverse by and setting the bundle location via React Native's debug menu to a local network IP/port (e.g. 192.168.1.20:8081), but as soon as ProxyMan was enabled as the proxy, React Native debugging broke. (as a side note I noticed that Charles Proxy does not exhibit this problem)

To work around the issue I made a Proxy auto-config script to tell Android to bypass the proxy for localhost only, while proxying all other hosts. This allowed me to work around the ProxyMan/websocket issue.

function FindProxyForURL(url, host) {
  if (host.indexOf('localhost') > -1) {
  	return null;
  }

  return "PROXY 192.168.1.60:9090";
}

[NghiaTranUIT]

Thanks for the update. I will try again to reproduce and fix it this weekend 👍

[yoniholmes]

Hi @Justin-Credible, thanks very much for raising this ticket and sharing your work around. Would you be able to elaborate on your Proxy auto-config solution? Where do you place this code / how is it run?

I'm facing a similar issue. My React Native app is successfully proxying all network traffic to Proxyman only what I believe are the metro bundler calls, /inspector, /message, /status are all resulting in Internal Error 999 and therefore the app returns an error saying that it cannot connect to the development server. ’adb reverse tcp:/8081 tcp:8081’ is not helping - hence would like to try to prevent these calls from proxying through Proxyman.

Many thanks to anyone in advance with any thoughts!

[Justin-Credible]

@yoniholmes

Sure, it looks like this:

1. Create a proxy.pac file with the contents of the above post
2. Change 192.168.1.60:9090 part of the script to be the IP/port of your Proxyman instance
3. Place proxy.pac on a webserver and ensure it is served with a Content-Type: application/x-ns-proxy-autoconfig response header
4. Edit the Android device's WiFi settings; set Proxy to Proxy Auto-Config
5. Enter the full URL to the proxy.pac file and save the changes

From now on, the contents of the proxy.pac script will execute for each URL to determine if it should be passed through the proxy or not. The simple script above will ignore any requests to localhost which should be the metro bundler. Everything else will be proxied.

Hope this helps!

[yoniholmes]

Thanks! I’ll give it a try. I managed to point my wifi config to a server hosting the pac file but I didn’t serve it with the Content-Type: application/x-ns-proxy-autoconfig header. Thanks for coming back to me! 🤞

On Fri, 17 Mar 2023 at 21:17, Justin Unterreiner @.***> wrote:

@yoniholmes https://github.com/yoniholmes

Sure, it looks like this:

1. Create a proxy.pac file with the contents of the above post https://github.com/ProxymanApp/Proxyman/issues/1407#issuecomment-1291126992
2. Change 192.168.1.60:9090 part of the script to be the IP/port of your Proxyman instance
3. Place proxy.pac on a webserver and ensure it is served with a Content-Type: application/x-ns-proxy-autoconfig response header
4. Edit the Android device's WiFi settings; set Proxy to Proxy Auto-Config
5. Enter the full URL to the proxy.pac file and save the changes

From now on, the contents of the proxy.pac script will execute for each URL to determine if it should be passed through the proxy or not. The simple script above will ignore any requests to localhost which should be the metro bundler. Everything else will be proxied.

Hope this helps!

— Reply to this email directly, view it on GitHub https://github.com/ProxymanApp/Proxyman/issues/1407#issuecomment-1474410933, or unsubscribe https://github.com/notifications/unsubscribe-auth/AABNCDOJZK4ADLDNNYUSUDTW4TIGFANCNFSM6AAAAAARKTROMY . You are receiving this because you were mentioned.Message ID: @.***>

[yoniholmes]

I managed to get this working. Steps:

1. Created an express server, hosting a proxy.pac, returning with a Content-Type: application/x-ns-proxy-autoconfig header, as per the contents shared above, i.e.:

function FindProxyForURL(url, host) {
  if (host.indexOf('localhost') > -1) {
  	return null;
  }
  if (host.indexOf('10.0.2.2') > -1) {
  	return null;
  }

  return "PROXY 192.168.1.60:9090"; // Replaced with my IP address 
}

2. Within my Android Emulator I disabled Mobile data, to ensure connectivity to the internet went solely through WiFi:

• Settings > Network & Internet > Mobile network > Mobile data (switched it off)

3. I then configured my Wifi Proxy to point to the pac file:

• Settings > Network & Internet > AndroidWifi > Pencil icon > Proxy (set to 'Proxy Auto-Config') > Pac URL (set to http://[my IP Address]:8080), note I don't specify proxy.pac in the URL

4. I then re-ran the 'Override Emulator' script from Proxyman (in Proxyman: Certificate > Install Certificate on Android > Emulators > Override Emulator

After this point all traffic from my Android was passing through Proxyman, and there were no issues with the Metro bundler failing to connect.

[yoniholmes]

So, while this worked for about a day - and what a glorious day it was - the setup later stopped working. I use a VPN so my IP address changed. But no amount of updating IP addresses have fixed the issue, so I can no longer inspect network traffic with Proxyman with my Android Emulator. I've spent at least a day trying to get it to work - but the Emulator consistently fails to attach to the metro bundler, both with and without the proxy.pac file in use.

Would be great if someone could share and insight or success with using Proxyman with Android. Many thanks in advance.

[NghiaTranUIT]

@yoniholmes do you have any current solution with other tools like Charles Proxy + React Native? Maybe I should look into it and make it easier 🤔

[yoniholmes]

Hi @NghiaTranUIT, thanks. I haven't tried Charles Proxy.

With React Native Debugger I can see most network calls. However, I cannot see network calls from web views (I can with Proxyman on iOS, and once on Android). Also, React Native Debugger doesn't let me modify requests or responses. I really like Scripting with Proxyman, and would love to use it to debug the Android specific bug I'm facing.

Only, as mentioned, I cannot get this to work. To be clear, Android can successfully pass traffic to Proxyman, which I can inspect. But the React Native app fails to connect to the metro bundler, which is a fatal error meaning I cannot test my app.

[NghiaTranUIT]

To intercept traffic from the Webview inside the Android app, you should check this doc: https://docs.proxyman.io/debug-devices/android-device#intercept-traffic-from-embedding-webview

---

Do you any sample React Native App that I can reproduce it?

@yoniholmes can I use https://reactnative.dev/ to create an app for testing?

[yoniholmes]

Re: Webview inpsection Actually this was working fine, I didn't need to make any further configuration changes

Re: Sample React Native App Yes that site should get you set up quite quickly. I don't have a sample app for you at the moment, and may not be able to set one up immediately.

[yoniholmes]

These are the errors I get. With Proxyman off, Android works fine.

[NghiaTranUIT]

@yoniholmes Can you try to add this IP to the Bypass list in the Wifi?

You can find it at System Setting -> Wifi -> Details -> Proxy -> Bypass Proxy Setting

[yoniholmes]

Sure I'll try that and let you know.

[NghiaTranUIT]

Just wondering what Proxyman for macOS version you're using?

I've tried on the latest build, and it seems the Metro is still working fine 🤔 I can update the App.js and hot-reload is still working.

• Only warning is Bridge was already shutdown.

[yoniholmes]

Thanks for sharing. I'm using Proxyman 4.5.0 (45000).

Still failing for me after putting 10.0.2.2 into my wifi proxy bypass settings.

I'm not sure whether Expo might play any role – that port 19000 looks to be related to Expo, which is used in the React Native quick start. My project doesn't use Expo, so am not sure whether that's a factor.

I've tried both with and without VPN. Traffic from Android is all proxying to Proxyman, but the metro bundler 10.0.2.2:8081 calls all fail with code 999, Status 'Internal Error'

The message in the 'Response' panel in Proxyman says:

The operation couldn't be completed.
(NIOCore.ChannelError error O.) (code=0)

[NghiaTranUIT]

@yoniholmes I found a solution for React Native via Metro Bundler 👍

Android Emulator

1. Open Proxyman -> Certificate -> Install for Android -> Emulator -> Click on the "Revert the Proxy"
2. Open Android Emulator -> Setting App -> Network -> Wifi -> Find a way to change the proxy
3. Change the HTTP Proxy manually by using the Proxyman IP & Port
4. Before saving, enter the localhost in the bypass Proxy List ✅

5. Done
6. The Bridge Was shutdown warning is gone ✅

Android Device

1. Open Android Emulator -> Setting App -> Network -> Wifi -> Find a way to change the proxy
2. Change the HTTP Proxy manually by using the Proxyman IP & Port
3. Before saving, enter the your IP in the bypass Proxy List ✅ . In your case, it's 10.0.2.2
4. Done

[yoniholmes]

Hi @NghiaTranUIT, yes! Thank you very much, I now have Android working with Proxyman. Truly appreciated, was stuck on this for a long time!

After making the manual WiFI proxy changes within Android (I'd switched off mobile data previously, so the only network I was using as the Emulator's WiFi network), along with the bypass settings (I added "localhost,10.0.2.2" to be sure, but I can test the difference later), then I could run my app, no metro bundler connectivity issues, and I could inspect network traffic from my app. 🎉

Without adding the res/xml/network_security_config.xml, the metro bundler would still connect, and I could see the domains that my app was calling, but I could not inspect them. After restoring the network_security_config.xml file, I could then run my Android app, no metro bundler issues, and I could inspect the calls being made from the app.

Thanks again & hope you enjoy the rest of your week!

[NghiaTranUIT]

Awesome, I will add my instruction to the React Native document page.

[coofzilla]

I was having a similar issue. Does the automated setup work with react-native ? Basically pressing this override emulator or do you have to manually add it in the actual settings of the emulator?

Also, do you have to add it to both settings?

Referencing this automated setup.

Current setup:

but then I get the same like above:

I tried those steps; but, still facing the same issue :/

Got it fixed

Can someone enlighten me as to why that is needed ? 🤔

[NghiaTranUIT]

@coofzilla:

Does the automated setup work with react-native ?

Yes, it's.

Basically pressing this override emulator or do you have to manually add it in the actual settings of the emulator?

You only either use the Emulator or manual setting for Android devices. Don't need to use twice.

Also, do you have to add it to both settings?

If you mean the step 3 that you modify the network.xml, it's required.

[coofzilla]

@NghiaTranUIT Thank you for the response, the only issue I have now is, when I quit proxyman. I have to undo everything to get it to work normally again. Conversely, setting up, I have to redo everything I just undid such as setting up all the local host stuff. Is that intended?

[NghiaTranUIT]

Yes, you have to revert all proxy settings if you don't use Proxyman on your emulator.

Please click on the Revert Button at the end 👍

---

Proxyman uses the adb command line to modify your Android emulator.

[MariuzM]

I don’t know on Android with RN+Expo nothing works for me :(

And tried again

Tried new emulator and just follow the steps for RN but nothing works