Failed to start DevTools: Dart DevTools exited with code 255
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Resolving 'Failed to start DevTools: Dart DevTools exited with code 255' in Flutter
Encountering the 'Dart DevTools exited with code 255' error can halt your Flutter development. This article provides comprehensive solutions to diagnose and fix this common issue, getting you back to efficient debugging.
The 'Failed to start DevTools: Dart DevTools exited with code 255' error is a frustrating message that many Flutter developers face. It typically indicates an issue with the DevTools application itself or its environment, preventing it from launching correctly. This can severely impact your ability to debug and inspect your Flutter applications. This article will guide you through various troubleshooting steps, from basic checks to more advanced solutions, to resolve this error.
Understanding the 'Exit Code 255' Error
Exit code 255 is a generic error code indicating a failure or an unhandled exception within a process. In the context of Dart DevTools, it means that the DevTools application, which is a web-based suite of debugging and performance tools for Dart and Flutter, failed to start or crashed during its initialization. This can be due to a variety of reasons, including corrupted installations, environment misconfigurations, port conflicts, or issues with the Dart SDK itself.
Potential causes and troubleshooting paths for DevTools error
Common Causes and Initial Checks
Before diving into complex solutions, it's crucial to rule out the most common and easily fixable issues. These often involve your Flutter and Dart SDK installations, as well as the DevTools package itself.
1. Step 1
Verify Flutter and Dart SDK Installation: Ensure your Flutter and Dart SDKs are properly installed and configured. Run flutter doctor in your terminal to check for any reported issues. Address any warnings or errors before proceeding.
2. Step 2
Update Flutter and Dart: Outdated versions can sometimes lead to incompatibilities. Update your Flutter SDK using flutter upgrade and then ensure Dart DevTools is also updated by running flutter pub global activate devtools.
3. Step 3
Clean Your Project: A corrupted build cache can sometimes interfere with DevTools. Navigate to your project directory and run flutter clean followed by flutter pub get.
4. Step 4
Restart Your IDE and System: Sometimes, a simple restart of your IDE (VS Code, Android Studio) or even your entire system can resolve transient issues.
flutter doctor
flutter upgrade
flutter pub global activate devtools
flutter clean
flutter pub get
Essential commands to perform initial diagnostics and updates.
Diagnosing and Resolving Deeper Issues
If the initial checks don't resolve the problem, the issue might be more deeply rooted. This section covers troubleshooting steps related to port conflicts, DevTools installation paths, and environment variables.
1. Step 1
Check for Port Conflicts: DevTools typically runs on port 9100. Another application might be using this port, preventing DevTools from starting. You can check port usage by running netstat -ano | findstr :9100 on Windows or lsof -i :9100 on macOS/Linux. If a process is using it, you can either terminate it or try to launch DevTools manually on a different port (though this is less straightforward when integrated with an IDE).
2. Step 2
Reinstall Dart DevTools Globally: A corrupted global installation of DevTools can cause this error. Uninstall and then reinstall it: flutter pub global deactivate devtools followed by flutter pub global activate devtools.
3. Step 3
Verify Environment Variables: Ensure that your system's PATH environment variable correctly includes the flutter/bin and dart/bin directories, as well as the ~/.pub-cache/bin directory where global Dart executables (like devtools) are stored. Incorrect PATH settings can prevent the system from finding the devtools executable.
4. Step 4
Manually Launch DevTools (for testing): To isolate if the issue is with your IDE integration or DevTools itself, try launching DevTools manually from the terminal. First, find its path using flutter pub global list to locate devtools. Then, run dart <path_to_devtools>/bin/devtools.dart or simply devtools if it's in your PATH. If it launches successfully, the issue might be with your IDE's integration.
5. Step 5
Review IDE Logs: Your IDE (VS Code or Android Studio) may provide more detailed error messages in its output or log windows. These logs can offer crucial clues about why DevTools failed to start.
Tab 1
### Tab 2
language: powershell
### Tab 3
title: Windows Port Check
### Tab 4
content: netstat -ano | findstr :9100
### Tab 5
Tab 6
### Tab 7
language: bash
### Tab 8
title: macOS/Linux Port Check
### Tab 9
content: lsof -i :9100
### Tab 10
flutter pub global deactivate devtools
flutter pub global activate devtools
Commands to deactivate and reactivate the global DevTools package.
devtools executable to your PATH for the current terminal session to test if it resolves the problem before making permanent system changes.