Unable to connect frontend and backend in MERN app. I was getting a "Network Error" after some changes I am now getting "Cannot GET /api/test/all"

Question

I am creating a role-based authentication MERN app with node.js express as backend and react as frontend. I tried to connect both backend and front following tutorials on https://www.bezkoder.com/react-jwt-auth/.

Here is some code snippets:

App.js file

import { BrowserRouter, Routes, Route, Link } from "react-router-dom";

import "bootstrap/dist/css/bootstrap.min.css";
import React, { Component } from "react";
import "./App.css";
import AuthService from "./services/auth.service";
import Login_ from "./components/login.component";
import Register from "./components/register.component";
import MainContent from "./components/main-content.component";
import Profile from "./components/profile.component";
import BoardUser from "./components/board-user.component";
import BoardAdmin from "./components/board-admin.component";



class App extends Component {
  constructor(props) {
    super(props);
    this.logOut = this.logOut.bind(this);
    this.state = {
      showModeratorBoard: false,
      showAdminBoard: false,
      currentUser: undefined,
    };
  }
  componentDidMount() {
    const user = AuthService.getCurrentUser();
    if (user) {
      this.setState({
        currentUser: user,
        showAdminBoard: user.roles.includes("ROLE_ADMIN"),
      });
    }
  }
  logOut() {
    AuthService.logout();
  }
  render() {
    const { currentUser, showAdminBoard } = this.state;
    return (
      <div>
        <nav className="navbar navbar-expand navbar-dark bg-dark">
          <Link to={"/"} className="navbar-brand">
            Network monitor
          </Link>
          <div className="navbar-nav mr-auto">
            <li className="nav-item">
              <Link to={"/home"} className="nav-link">
                Home
              </Link>
            </li>
            {showAdminBoard && (
              <li className="nav-item">
                <Link to={"/admin"} className="nav-link">
                  Admin Board
                </Link>
              </li>
            )}
            {currentUser && (
              <li className="nav-item">
                <Link to={"/user"} className="nav-link">
                  User
                </Link>
              </li>
            )}
          </div>
          {currentUser ? (
            <div className="navbar-nav ml-auto">
              <li className="nav-item">
                <Link to={"/profile"} className="nav-link">
                  {currentUser.username}
                </Link>
              </li>
              <li className="nav-item">
                <a href="/login" className="nav-link" onClick={this.logOut}>
                  LogOut
                </a>
              </li>
            </div>
          ) : (
            <div className="navbar-nav ml-auto">
              <li className="nav-item">
                <Link to={"/login"} className="nav-link">
                  Login
                </Link>
              </li>
              <li className="nav-item">
                <Link to={"/register"} className="nav-link">
                  Sign Up
                </Link>
              </li>
            </div>
          )}
        </nav>
        <div className="container mt-3">
          <Routes>
            <Route path="/" element={<MainContent/>} />
            <Route path="/login" element={<Login_/>} />
            <Route path="/register" element={<Register/>} />
            <Route exact path="/profile" element={<Profile/>} />
            <Route path="/user" element={<BoardUser/>} />
            <Route path="/admin" element={<BoardAdmin/>} />
          </Routes>
        </div>
      </div>
    );
  }
}
export default App;

here is my index.js file:

import React from 'react';
import ReactDOM from 'react-dom/client';
import App from './App';
import { DarkModeContextProvider } from './context/darkModeContext';
import { BrowserRouter } from "react-router-dom";


const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
    <DarkModeContextProvider>
      <BrowserRouter>
      <App />
      </BrowserRouter>
    </DarkModeContextProvider>
);

server.js

const express = require("express");
const cors = require("cors");
//const dbConfig = require("./src/configuration/db.config");
const app = express();
var corsOptions = {
  origin: "http://localhost:8081"
};
app.use(cors(corsOptions));
// parse requests of content-type - application/json
app.use(express.json());
// parse requests of content-type - application/x-www-form-urlencoded
app.use(express.urlencoded({ extended: false }));

const db = require("./src/models");
const Role = db.role;
const path = "mongodb+srv://ciaran_barber:[email protected]/project_db?retryWrites=true&w=majority";
db.mongoose
  .connect(path, { useNewUrlParser: true, useUnifiedTopology: true
  })
  /*.connect(`mongodb://${dbConfig.HOST}:${dbConfig.PORT}/${dbConfig.DB}`, {
    useNewUrlParser: true,
    useUnifiedTopology: true
    }) */
  .then(() => {
    console.log("Successfully connect to MongoDB.");
    initial();
  })
  .catch(err => {
    console.error("Connection error", err);
    process.exit();
  });

// simple route
app.get("/", (req, res) => {
  res.json({ message: "Welcome to Ciaran's web server." });
});

// routes
require("./src/routes/auth.routes")(app);
require("./src/routes/user.routes")(app);

// set port, listen for requests
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}.`);
});


function initial() {
  Role.estimatedDocumentCount((err, count) => {
    if (!err && count === 0) {
      new Role({
        name: "user"
      }).save(err => {
        if (err) {
          console.log("error", err);
        }
        console.log("added 'user' to roles collection");
      });
      new Role({
        name: "admin"
      }).save(err => {
        if (err) {
          console.log("error", err);
        }
        console.log("added 'admin' to roles collection");
      });
    }
  });
}

package.json file:

{
  "name": "final_year_project_b00759858",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@babel/core": "^7.16.0",
    "@emotion/react": "^11.9.0",
    "@emotion/styled": "^11.8.1",
    "@mui/icons-material": "^5.6.2",
    "@mui/material": "^5.6.2",
    "@mui/x-data-grid": "^5.10.0",
    "@pmmmwh/react-refresh-webpack-plugin": "^0.5.3",
    "@svgr/webpack": "^5.5.0",
    "@testing-library/jest-dom": "^5.16.4",
    "@testing-library/react": "^13.1.1",
    "@testing-library/user-event": "^13.5.0",
    "axios": "^0.27.2",
    "babel-jest": "^27.4.2",
    "babel-loader": "^8.2.3",
    "babel-plugin-named-asset-import": "^0.3.8",
    "babel-preset-react-app": "^10.0.1",
    "bcryptjs": "^2.4.3",
    "bfj": "^7.0.2",
    "bootstrap": "^5.1.3",
    "browserslist": "^4.18.1",
    "camelcase": "^6.2.1",
    "case-sensitive-paths-webpack-plugin": "^2.4.0",
    "concurrently": "^7.1.0",
    "cors": "^2.8.5",
    "css-loader": "^6.5.1",
    "css-minimizer-webpack-plugin": "^3.2.0",
    "dotenv": "^10.0.0",
    "dotenv-expand": "^5.1.0",
    "eslint": "^8.3.0",
    "eslint-config-react-app": "^7.0.1",
    "eslint-webpack-plugin": "^3.1.1",
    "express": "^4.18.0",
    "file-loader": "^6.2.0",
    "fs-extra": "^10.0.0",
    "html-webpack-plugin": "^5.5.0",
    "identity-obj-proxy": "^3.0.0",
    "jest": "^27.4.3",
    "jest-resolve": "^27.4.2",
    "jest-watch-typeahead": "^1.0.0",
    "jsonwebtoken": "^8.5.1",
    "koala": "^1.0.0",
    "mini-css-extract-plugin": "^2.4.5",
    "mongoose": "^6.3.1",
    "nodemon": "^2.0.16",
    "postcss": "^8.4.4",
    "postcss-flexbugs-fixes": "^5.0.2",
    "postcss-loader": "^6.2.1",
    "postcss-normalize": "^10.0.1",
    "postcss-preset-env": "^7.0.1",
    "prompts": "^2.4.2",
    "react": "^18.0.0",
    "react-app-polyfill": "^3.0.0",
    "react-dev-utils": "^12.0.1",
    "react-dom": "^18.0.0",
    "react-refresh": "^0.11.0",
    "react-router": "^6.3.0",
    "react-router-dom": "^6.3.0",
    "react-validation": "^3.0.7",
    "resolve": "^1.20.0",
    "resolve-url-loader": "^4.0.0",
    "sass": "^1.50.1",
    "semver": "^7.3.5",
    "source-map-loader": "^3.0.0",
    "style-loader": "^3.3.1",
    "tailwindcss": "^3.0.2",
    "terser-webpack-plugin": "^5.2.5",
    "validator": "^13.7.0",
    "web-vitals": "^2.1.4",
    "webpack-dev-server": "^4.6.0",
    "webpack-manifest-plugin": "^4.0.2",
    "workbox-webpack-plugin": "^6.4.1"
  },
  "scripts": {
    "start": "nodemon scripts/start.js",
    "build": "node scripts/build.js",
    "test": "node scripts/test.js"
  },
  "eslintConfig": {
    "extends": [
      "react-app",
      "react-app/jest"
    ]
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "jest": {
    "roots": [
      "<rootDir>/src"
    ],
    "collectCoverageFrom": [
      "src/**/*.{js,jsx,ts,tsx}",
      "!src/**/*.d.ts"
    ],
    "setupFiles": [
      "react-app-polyfill/jsdom"
    ],
    "setupFilesAfterEnv": [],
    "testMatch": [
      "<rootDir>/src/**/__tests__/**/*.{js,jsx,ts,tsx}",
      "<rootDir>/src/**/*.{spec,test}.{js,jsx,ts,tsx}"
    ],
    "testEnvironment": "jsdom",
    "transform": {
      "^.+\\.(js|jsx|mjs|cjs|ts|tsx)$": "<rootDir>/config/jest/babelTransform.js",
      "^.+\\.css$": "<rootDir>/config/jest/cssTransform.js",
      "^(?!.*\\.(js|jsx|mjs|cjs|ts|tsx|css|json)$)": "<rootDir>/config/jest/fileTransform.js"
    },
    "transformIgnorePatterns": [
      "[/\\\\]node_modules[/\\\\].+\\.(js|jsx|mjs|cjs|ts|tsx)$",
      "^.+\\.module\\.(css|sass|scss)$"
    ],
    "modulePaths": [],
    "moduleNameMapper": {
      "^react-native$": "react-native-web",
      "^.+\\.module\\.(css|sass|scss)$": "identity-obj-proxy"
    },
    "moduleFileExtensions": [
      "web.js",
      "js",
      "web.ts",
      "ts",
      "web.tsx",
      "tsx",
      "json",
      "web.jsx",
      "jsx",
      "node"
    ],
    "watchPlugins": [
      "jest-watch-typeahead/filename",
      "jest-watch-typeahead/testname"
    ],
    "resetMocks": true
  },
  "babel": {
    "presets": [
      "react-app"
    ]
  },
  "devDependencies": {
    "node-sass": "^7.0.1",
    "sass-loader": "^12.6.0",
    "webpack": "^5.72.0"
  }
}

EDIT: Also if I "proxy": "http://127.0.0.1:8080/", to package.json file I get this error:

"Proxy error: Could not proxy request /api/test/all from localhost:8081 to http://127.0.0.1:8080/. See https://nodejs.org/api/errors.html#errors_common_system_errors for more information (ECONNREFUSED)."