Port 8081 is already in use
Error:- Another Metro bundler instance is running.
- A previous Fast Refresh session didn’t terminate properly.
- Another app is using port 8081.
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Find the process that uses port 8081:
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End the specific process or all processes on port 8081:
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Restart Metro:
App not reflecting changes
Cause: Fast Refresh fails to show code changes when you use the wrong build variant for your device’s architecture. Each device requires a specific debug build type to properly support Fast Refresh functionality. Solution: Use the correct debug build variant for your device:- Fire TV Device: Use
*_armv7.vpkg - Mac Intel Vega Virtual Device: Use
*_x86_64.vpkg - Mac M1/M2 Vega Virtual Device: Use
*_aarch64.vpkg
No connection to Metro Server
Cause: The Metro Server can’t connect to your device, which prevents Fast Refresh from functioning. A “Pending… Device connection” message in the Metro Server indicates a connection failure. Solution:- Verify if port forwarding is active.
- Check if your device serial number is correct.
- Make sure both terminals (Metro Server and app) are running.
- Confirm you’re using port 8081 for the Metro Server connection.
Architecture mismatch
Cause: The app crashes or fails to launch due to a mismatch between the device architecture and the built app package (.vpkg file). The mismatch occurs when you compile the app for a different architecture than the one your device uses.
Solution:
- Check if your device architecture matches the .vpkg file.
- Use
kepler device infocommand to verify the device architecture. - If there’s a mismatch, rebuild your app with the correct architecture.
