Appium Inspector Fails to Connect to Flutter App Due to Dynamically Changing Dart Observatory URL

[sai9133]

I'm using Appium Inspector to automate testing of a Flutter app on an Android emulator. However, I keep encountering an issue where the Dart Observatory URL dynamically changes each time I launch the app, causing the session to fail with the following error:

Error Failed to create session. An unknown server-side error occurred while processing the command. Original error: Cannot connect to the Dart Observatory URL ws://127.0.0.1:41145/JbqYpXh-u2E=/ws. Check the server log for more details

Context: Platform: Android Emulator Appium Version: 2.11.3 Flutter Version:3.24.0

What I’ve Tried: Port Forwarding: I've manually forwarded the dynamic Dart Observatory port to a static port using:

cmd :

adb forward tcp:3000 tcp:[DYNAMIC_PORT]

This works temporarily, but since the Dart VM service port changes every time the app restarts, I have to repeat this process constantly.

Setting a Static Port: I don't have access to the source code, so I'm unable to modify the Dart VM settings to use a static port.

My Questions: ->Is there a way to stabilize the Dart Observatory port without access to the app's source code? ->Can Appium be configured to automatically detect and handle the dynamic Dart VM port? A->re there alternative approaches or tools that might handle Flutter app testing more reliably in this scenario? ->Any guidance on how to consistently connect Appium to the Dart Observatory URL or alternative solutions would be greatly appreciated!

[KazuCocoa]

Could you share the full Appium server log?

Usually this driver scans the observatory port in the settings and configures the port-forwarding internally.

[JonathanMF2020]

Hey! I ran into the same issue while automating Flutter apps on Android emulators — that dynamic Dart Observatory URL can be quite a headache when trying to maintain session stability.

I added the following capability to my Appium configuration

"appium:maxRetryCount": "20"

This allows Appium to retry several times while waiting for the Dart Observatory to be ready, automatically handling the dynamic port changes.

{
  "appium:platformName": "Android",
  "appium:automationName": "Flutter",
  "appium:deviceName": "emulator-5554",
  "appium:appPackage": "com.example.appium_test",
  "appium:maxRetryCount": "20"
}

Since the Dart VM port changes every time the app restarts and you don’t have access to set a static one, this retry mechanism acts as a workaround, giving Appium enough time to detect and connect to the new URL without having to manually run the adb forward command each time.

[BelalNayzak]

@sai9133 I'm facing the same issue appium / Dart VM port missmatch!

I tried 1 step futher (I dont know if would work in your case but let me know if you have any update)

try to run the app with this command

flutter run -d emulator-5554 --debug --disable-service-auth-codes

replace the "emulator-5554" with your emulator/device id

to know the device id run this command

adb devices

[BelalNayzak]

@JonathanMF2020 I tried your solution but didnt work, i still have the same issue

[BelalNayzak]

@KazuCocoa is there any solution for that ?
the driver can't properly detect the Dart VM Service port dynamically! i always get a missmatch between the port that appium trying to deal with and the port that the app is running on!