"flutter attach" fails to connect when using --debug-url

If I run a Flutter app with flutter run:

danny@Dannys-MacBook-Pro src % flutter run         
// ...
An Observatory debugger and profiler on Android SDK built for x86 is available at: http://127.0.0.1:55772/yRmpm6wAk9w=/
The Flutter DevTools debugger and profiler on Android SDK built for x86 is available at: http://127.0.0.1:9101?uri=http://127.0.0.1:55772/yRmpm6wAk9w=/

And then try to connect to it using flutter attach with --debug-url, it fails:

danny@Dannys-MacBook-Pro src % flutter attach -d emulator-5554 --debug-url http://127.0.0.1:55772/yRmpm6wAk9w=/
Error connecting to the service protocol: failed to connect to http://127.0.0.1:55918/yRmpm6wAk9w=/

(note the port number in the error is different to the one I provided)

Connecting using the device (-d) seems to work fine.

Passing --debug-url is a workflow supported in VS Code to allow users to attach to Flutter apps that might have been launched externally from VS Code, but currently this fails for the reasons above.

I believe this used to work at some point in the past, because #70847 looks like a fix for a very similar issue, however even if I pass --no-dds to both flutter run and flutter attach here, I see the same failure.

@DanTup

Hello @DanTup. Thank you for filling this issue. I can reproduce this issue with the default counter app.

Reproducible on:

Stable (3.0.5)
Beta (3.3.0-0.5.pre)
Master (3.1.0-0.0.pre.2481)

Commands run

> flutter run

An Observatory debugger and profiler on sdk gphone64 x86 64 is available at: http://127.0.0.1:65415/yqkdOMccHd4=/
The Flutter DevTools debugger and profiler on sdk gphone64 x86 64 is available at: http://127.0.0.1:9101?uri=http://127.0.0.1:65415/yqkdOMccHd4=/

> flutter attach --debug-url "http://127.0.0.1:65415/yqkdOMccHd4=/"

Error connecting to the service protocol: failed to connect to http://127.0.0.1:65476/yqkdOMccHd4=/

Doctor Output

flutter doctor -v (Stable)

[✓] Flutter (Channel stable, 3.0.5, on Microsoft Windows [Version 10.0.22000.856], locale en-IN)
    • Flutter version 3.0.5 at C:\Users\Nabeel\fvm\versions\stable
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision f1875d570e (6 weeks ago), 2022-07-13 11:24:16 -0700
    • Engine revision e85ea0e79c
    • Dart version 2.17.6
    • DevTools version 2.12.2

[✗] Android toolchain - develop for Android devices
    ✗ Unable to locate Android SDK.
      Install Android Studio from: https://developer.android.com/studio/index.html
      On first launch it will assist you in installing the Android SDK components.
      (or visit https://flutter.dev/docs/get-started/install/windows#android-setup for detailed instructions).
      If the Android SDK has been installed to a custom location, please use
      `flutter config --android-sdk` to update to that location.


[✓] Chrome - develop for the web
    • CHROME_EXECUTABLE = C:\Program Files\BraveSoftware\Brave-Browser\Application\brave.exe

[✓] Visual Studio - develop for Windows (Visual Studio Community 2022 17.2.6)
    • Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
    • Visual Studio Community 2022 version 17.2.32630.192
    • Windows 10 SDK version 10.0.19041.0

[!] Android Studio (not installed)
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/docs/get-started/install/windows#android-setup for detailed instructions).

[✓] VS Code (version 1.70.2)
    • VS Code at C:\Users\Nabeel\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension can be installed from:
      🔨 https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.22000.856]
    • Chrome (web)      • chrome  • web-javascript • unknown
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 104.0.1293.63

[✓] HTTP Host Availability
    • All required HTTP hosts are available

! Doctor found issues in 2 categories.

flutter doctor -v (Master)

[✓] Flutter (Channel master, 3.1.0-0.0.pre.2481, on Microsoft Windows [Version 10.0.22000.856], locale en-IN)
    • Flutter version 3.1.0-0.0.pre.2481 on channel master at C:\Users\Nabeel\fvm\versions\master
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 91fdbfa7c8 (4 hours ago), 2022-08-25 03:07:06 -0400
    • Engine revision 9600c6c39b
    • Dart version 2.19.0 (build 2.19.0-137.0.dev)
    • DevTools version 2.16.0

[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
    • Android SDK at C:\android-sdk
    • Platform android-33, build-tools 33.0.0
    • Java binary at: C:\Program Files\Java\jdk-17.0.4\bin\java
    • Java version Java(TM) SE Runtime Environment (build 17.0.4+11-LTS-179)
    • All Android licenses accepted.

[✓] Chrome - develop for the web
    • CHROME_EXECUTABLE = C:\Program Files\BraveSoftware\Brave-Browser\Application\brave.exe

[✓] Visual Studio - develop for Windows (Visual Studio Community 2022 17.2.6)
    • Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
    • Visual Studio Community 2022 version 17.2.32630.192
    • Windows 10 SDK version 10.0.19041.0

[!] Android Studio (not installed)
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/docs/get-started/install/windows#android-setup for detailed instructions).

[✓] VS Code (version 1.70.2)
    • VS Code at C:\Users\Nabeel\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension can be installed from:
      🔨 https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.22000.856]
    • Chrome (web)      • chrome  • web-javascript • unknown
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 104.0.1293.63

[✓] HTTP Host Availability
    • All required HTTP hosts are available

! Doctor found issues in 1 category.

Reading the code here:

flutter/packages/flutter_tools/lib/src/commands/attach.dart

Lines 307 to 316 in 91fdbfa

    
           observatoryUri = Stream<Uri> 
        
             .fromFuture( 
        
               buildObservatoryUri( 
        
                 device, 
        
                 debugUri?.host ?? hostname, 
        
                 debugPort ?? debugUri!.port, 
        
                 hostVmservicePort, 
        
                 debugUri?.path, 
        
               ) 
        
             ).asBroadcastStream();

Which calls here:

flutter/packages/flutter_tools/lib/src/mdns_discovery.dart

Line 245 in 91fdbfa

Future<Uri> buildObservatoryUri(

It looks like --debug-url might expect a device port, and not the host port. So I think it's setting up a new forwarded port to the supplied port on the device (where nothing is listening). It's possible that what I'm trying to do here is not supported (usually you'd use flutter attach with an app not launched with flutter run). If that's the case, the fix may be just to improve the description on --debug-url to make this clearer:

flutter/packages/flutter_tools/lib/src/commands/attach.dart

Lines 82 to 84 in 91fdbfa

    
           'debug-url', 
        
           aliases: <String>[ 'debug-uri' ], // supported for historical reasons 
        
           help: 'The URL at which the observatory is listening.',

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"flutter attach" fails to connect when using --debug-url #110260

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	observatoryUri = Stream<Uri>
	.fromFuture(
	buildObservatoryUri(
	device,
	debugUri?.host ?? hostname,
	debugPort ?? debugUri!.port,
	hostVmservicePort,
	debugUri?.path,
	)
	).asBroadcastStream();

	'debug-url',
	aliases: <String>[ 'debug-uri' ], // supported for historical reasons
	help: 'The URL at which the observatory is listening.',

"flutter attach" fails to connect when using --debug-url #110260

Description

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exaby73 commented on Aug 25, 2022

Reproducible on:

Commands run

Doctor Output

DanTup commented on Aug 25, 2022

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