Connection refused when launching Electron app generated with electron-packager/ electron-builder - electron

Question

I have a React Electron app with Webpack and try to build it into an executable.
I used the CLI commands of electron-packager and electron-builder which ran without errors.
But when I run the exe I get a blank screen and from terminal the error message:
(node:8172) electron: Failed to load URL: http://localhost:3000/main_window with error: ERR_CONNECTION_REFUSED
(Use mixmatch --trace-warnings ... to show where the warning was created)
Running with the option doesn't give any additional information.
Searching the source code for localhost leads to index.js in the webpack directory:
var createWindow = function () {
var preload = path_1.default.join(__dirname, '../renderer/main_window', "preload.js");
exports.mainWindow = new electron_1.BrowserWindow({
// show: false,
webPreferences: {
enableRemoteModule: false,
// nodeIntegration: false, // is default value after Electron v5
preload: preload // use a preload script
}
});
exports.mainWindow.loadURL('http://localhost:3000/main_window');
exports.mainWindow.maximize();
exports.mainWindow.webContents.openDevTools();
};
So I guess a server is being started, which probably is the same for every app, but the app is not allowed to access localhost.
So why does it seem to work easily for everyone else but not for me?

Answer 1

Once the build is created, you need to loadURL from build/index.html.
Replace your code of export.mainWindow.loadURL with this
e.g.
const isDev = require('electron-is-dev');
exports.mainWindow.loadURL(
isDev
? 'http://localhost:3000'
: `file://${path.join(__dirname, '../build/index.html')}`
);