Could not connect to React Native development server on Android

Question

When I run react-native run-android, it gives me the following error:

Could not connect to development server

• Package server is running and I can access it directly from browser on my mobile device.
• My Android device is connected to computer and has debugging enabled (I checked using adb devices command).
• My Android version is 4.4.4 so I cannot use adb reverse command.
• I have set the ID address and port in Dev setting.
• USB debug is on.
• I use Windows 7.

How to fix this error?

Answer 1

In my case the problem was with Android security policies. According to the documentation:

Starting with Android 9.0 (API level 28), cleartext support is disabled by default.

But the application tries to access Metro Bundler through HTTP, right? And that's why it can't. In order to enable cleartext traffic, open your AndroidManifest.xml and add android:usesCleartextTraffic="true" to <application> node.

For example:

<application
    android:name="com.example.app"
    android:allowBackup="false"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme"
    android:usesCleartextTraffic="true">

You can find more solutions in this SO: https://stackoverflow.com/a/50834600/1673320. OP's problem is different, but similar.