ADB

ADB, the Android Debug Bridge, is the command-line tool from the Android SDK platform-tools that connects your computer to Android devices and the Android Emulator. Every time a React Native app is installed or launched on Android during development, ADB is doing the work underneath.

It has three parts: the adb client you type commands into, a background server on your machine, and a daemon running on each device. The commands a React Native developer uses most:

adb devices                      # list connected devices and emulators
adb reverse tcp:8081 tcp:8081    # let the device reach Metro on your machine
adb logcat                       # stream native logs, including crashes
adb install app-release.apk      # sideload a build
adb shell input keyevent 82      # open the Dev Menu on a device

adb reverse matters most. A phone’s localhost is the phone itself, so without that port mapping the app cannot download the bundle from Metro. The CLI runs it automatically, but it resets when a USB cable is reconnected or the server restarts; rerun it when you hit "could not connect to development server". With several devices attached, add -s <serial> to target one.

adb logcat is the first place to look when an Android build crashes on launch before JavaScript runs: native exceptions never reach the JS console.

Common gotchas:

• "adb server version doesn’t match this client" means two copies of ADB are installed, often one from Android Studio and one from Homebrew. Keep one on your PATH.
• "unauthorized" devices need the USB debugging prompt accepted on the phone.
• Physical devices need Developer options and USB debugging switched on first.

See the ADB docs.