expo ios simulator 'could not connect to development server' error(works on browser)

Question

I was developing a chat app in practice using react-native expo, but when I suddenly executed "expo start" in the usual development flow, the error "could not connect to development server" was displayed.

If you have experienced the same error and know a solution, I would appreciate it if you could help.

Since I was linking with aws-amplify just before, I thought that the one installed due to that relationship was the cause of the error, but since the application starts normally in the browser, only the iOS simulator does not work (Android is in a situation where it downloads endlessly and does not start)

What I tried

1)Delete the cache with expo start -c

2)As the error says, npm start and then reload is repeated.

3)Delete 19000 with the kill command, thinking that it is a port problem. ・ Npm install ・ Rm -rf node_modules / && rm -rf yarn_lock / && yarn install && cd ios && pod install

Nothing worked, I cannot come up with any good idea to solve it. All solutions from the research are failed. What else could I do?

Referenced links

Could not connect to React Native development server on Android

Could not connect to the development server react native ios simulator Node

package.json↓

{
  "main": "node_modules/expo/AppEntry.js",
  "scripts": {
    "start": "expo start",
    "android": "expo start --android",
    "ios": "expo start --ios",
    "web": "expo start --web",
    "eject": "expo eject",
    "test": "jest --watchAll"
  },
  "jest": {
    "preset": "jest-expo"
  },
  "dependencies": {
    "-": "^0.0.1",
    "@expo/vector-icons": "^12.0.0",
    "@react-native-async-storage/async-storage": "^1.15.11",
    "@react-native-community/masked-view": "0.1.10",
    "@react-native-community/netinfo": "^6.2.1",
    "@react-navigation/bottom-tabs": "5.11.2",
    "@react-navigation/native": "~5.8.10",
    "@react-navigation/stack": "~5.12.8",
    "aws-amplify": "^4.3.6",
    "aws-amplify-react-native": "^6.0.1",
    "cli": "^1.0.1",
    "expo": "~42.0.1",
    "expo-asset": "~8.3.2",
    "expo-constants": "~11.0.1",
    "expo-font": "~9.2.1",
    "expo-linking": "~2.3.1",
    "expo-splash-screen": "~0.11.2",
    "expo-status-bar": "~1.0.4",
    "expo-web-browser": "~9.2.0",
    "g": "^2.0.1",
    "react": "16.13.1",
    "react-dom": "16.13.1",
    "react-native": "https://github.com/expo/react-native/archive/sdk-42.0.0.tar.gz",
    "react-native-gesture-handler": "~1.10.2",
    "react-native-reanimated": "~2.2.0",
    "react-native-safe-area-context": "3.2.0",
    "react-native-screens": "~3.4.0",
    "react-native-web": "~0.13.12"
  },
  "devDependencies": {
    "@babel/core": "^7.9.0",
    "@types/react": "~17.0.21",
    "@types/react-native": "~0.64.12",
    "jest-expo": "~41.0.0-beta.0",
    "typescript": "~4.3.5"
  },
  "private": true
}

Answer 1

I have met exactly the same issue when I am using amplify.

First, you should not only look at the expo console but also the terminal.

If the terminal said there are duplicated files in your project, delete one of them, and clear all cache & restart by expo start -c command.

I guess this issue cause that amplify is smarter than we are, so they automatically create backup files etc, and expo misunderstands them as a duplicated.

However, including deleting cache, this way worked, so I am not 100% sure.

If this solves, I would be happy.