Flutter 2: Error connecting to the service protocol: failed to connect to http://127.0.0.1:1039/ #58588

Question

I'm experiencing an issue with the Flutter template app when launching it on Flutter 2.0.3. I'm getting this output

Launching lib/main.dart on SM J320H in debug mode...
Running Gradle task 'assembleDebug'...
✓ Built build/app/outputs/flutter-apk/app-debug.apk.
Installing build/app/outputs/flutter-apk/app.apk...
Error connecting to the service protocol: failed to connect to http://127.0.0.1:62719/OJaWBfEtnmY=/

I'm launching this app on a real Android device. When launching with Flutter 1.22.5 - everything works fine.

Flutter doctor output:

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.0.3, on Mac OS X 10.15.7 19H2 darwin-x64, locale
    en-UA)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] IntelliJ IDEA Ultimate Edition (version 2020.1.1)
[✓] VS Code (version 1.54.3)
[✓] Connected device (2 available)

• No issues found!

Answer 1

I just got the same problem. It's because of your dart and flutter versions I guess.

Just run flutter upgrade and flutter clean to solve the problem.

Similar problem solutions here: https://github.com/flutter/flutter/issues/47204

This helped me. Here is the log:

PS D:\Documents\Work\bus_stop_routes> flutter clean
Deleting build...                                                  629ms
Deleting .dart_tool...                                             567ms
Deleting .packages...                                                0ms
Deleting Generated.xcconfig...                                       0ms
Deleting flutter_export_environment.sh...                            0ms
Deleting .flutter-plugins-dependencies...                            0ms
Deleting .flutter-plugins...                                         0ms
PS D:\Documents\Work\bus_stop_routes> flutter pub get
Running "flutter pub get" in bus_stop_routes...                     3.4s
PS D:\Documents\Work\bus_stop_routes> flutter run
Launching lib\main.dart on SM N910H in debug mode...
Note: C:\flutter\.pub-cache\hosted\pub.dartlang.org\google_maps_flutter-2.0.1\android\src\main\java\io\flutter\plugins\googlemaps\Convert.java uses or overrides a deprecated API.
Running Gradle task 'assembleDebug'...
Running Gradle task 'assembleDebug'... Done                        46.3s
√ Built build\app\outputs\flutter-apk\app-debug.apk.
Installing build\app\outputs\flutter-apk\app.apk...                29.0s
Activating Dart DevTools...                                         3.1s
Error connecting to the service protocol: failed to connect to http://127.0.0.1:58851/a7SAG7gM8aI=/
PS D:\Documents\Work\bus_stop_routes> dart upgrade
Could not find a command named "upgrade".

Usage: dart [<vm-flags>] <command|dart-file> [<arguments>]

Global options:
-h, --help                 Print this usage information.
-v, --verbose              Show additional command output.
    --version              Print the Dart SDK version.
    --enable-analytics     Enable anonymous analytics.
    --disable-analytics    Disable anonymous analytics.

Available commands:
  analyze   Analyze the projects Dart code.
  compile   Compile Dart to various formats.
  create    Create a new project.
  fix       Apply automated fixes to Dart source code.
  format    Idiomatically format Dart source code.
  migrate   Perform a null safety migration on a project or package.
  pub       Work with packages.
  run       Run a Dart program.
  test      Run tests in this package.

Run "dart help <command>" for more information about a command.
See https://dart.dev/tools/dart-tool for detailed documentation.
PS D:\Documents\Work\bus_stop_routes> flutter upgrade
Upgrading Flutter to 2.0.4 from 2.0.3 in C:\flutter...
Checking Dart SDK version... 
Downloading Dart SDK from Flutter engine 2dce47073a378673f6ca095e91b8065544c3a881...       
Building flutter tool... 
Running pub upgrade... 

Upgrading engine...
Downloading android-arm-profile/windows-x64 tools...               20.1s
Downloading android-arm-release/windows-x64 tools...                8.7s
Downloading android-arm64-profile/windows-x64 tools...              9.7s
Downloading android-arm64-release/windows-x64 tools...              8.2s
Downloading android-x64-profile/windows-x64 tools...                9.3s
Downloading android-x64-release/windows-x64 tools...                7.9s
Downloading android-x86 tools...                                   98.3s
Downloading android-x64 tools...                                   64.8s
Downloading android-arm tools...                                   15.6s
Downloading android-arm-release tools...                           12.4s
Downloading android-arm64 tools...                                 36.2s
Downloading android-arm64-profile tools...                         18.1s
Downloading android-arm64-release tools...                         14.6s
Downloading android-x64-profile tools...                           19.0s
Downloading android-x64-release tools...                           15.0s
Downloading android-x86-jit-release tools...                       21.6s
Downloading Web SDK...                                             42.0s

Flutter 2.0.4 • channel stable • https://github.com/flutter/flutter.git
Framework • revision b1395592de (7 days ago) • 2021-04-01 14:25:01 -0700
Engine • revision 2dce47073a
Tools • Dart 2.12.2

Running flutter doctor...
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 2.0.4, on Microsoft Windows [Version 10.0.19042.867], locale en-US)
[√] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[√] Chrome - develop for the web
[√] Android Studio (version 4.1.0)
[√] VS Code (version 1.55.0)
[√] Connected device (3 available)

• No issues found!
PS D:\Documents\Work\bus_stop_routes> flutter run
Running "flutter pub get" in bus_stop_routes...                  1,114ms
Launching lib\main.dart on SM N910H in debug mode...
Running Gradle task 'assembleDebug'...                                  
Running Gradle task 'assembleDebug'... Done                       107.2s
√ Built build\app\outputs\flutter-apk\app-debug.apk.
Installing build\app\outputs\flutter-apk\app.apk...                29.2s
Syncing files to device SM N910H...                                141ms

Flutter run key commands.
r Hot reload.
R Hot restart.
h Repeat this help message.
d Detach (terminate "flutter run" but leave application running).
c Clear the screen
q Quit (terminate the application on the device).
An Observatory debugger and profiler on SM N910H is available at:
http://127.0.0.1:60828/axOQuzsu83M=/

If not solved, it's about the extension that you using.

• Please reopen your editor after this. But sometimes that not working when you use extensions.

• I also checked the virus defender. And allowed the permission.

Answer 2

I experience this issue when I add certain plugins or when I open the project in both Visual Studio Code and Android Studio.

If all other attempts to resolve this issue fails, restart your test device. This has worked for me.