```

const express = require('express');

const app = express();

app.use(express.json());

app.get('/', (req, res) => {

const data = {'message': 'Hello World!'}

res.send(data);

});

app.listen(3000, () => {

console.log('Listening on 3000');

});

```

This is an example Express server that listens for requests on port 3000 and responds with a JSON object containing the message "Hello World!". You can test it by opening your web browser and going to `http://localhost:3000`.