No apps connected. Sending "devMenu" to all React Native apps failed

Question

This is a strange error when I ran React Native (0.63.2) app on Android 8.1 emulator with

npx react-native run-android

Here is the full warning message:

warn No apps connected. Sending "devMenu" to all React Native apps failed. Make sure your app is running in the simulator or on a phone connected via USB.
info Opening developer menu...

Tried adb reverse tcp:8081 tcp:8081 but didn't help. The emulator was working fine. What can go wrong here?

Answer 1

Note: Answer targets only those visitors, who are facing this issue after successfully running once on device

npx react-native run-android
//once its installed on device next time just do
npx react-native start

installs app at your device on first run. I was facing same issue only when I tried npx react-native run-android second time.

So I used npx react-native start then

I just opened my latest app installed by last run and its working and showing me the updates as well