How to make Vrlin APP

**Python (`app.py`):**

```python
from flask import Flask, request
from flask_cors import CORS
from tkinter import Tk, messagebox
import threading

app = Flask(__name__)

CORS(app, origins="*")

def show_popup(text):
    root = Tk()
    root.withdraw()

# Make the dialog appear on top
    root.attributes("-topmost", True)
    root.lift()
    root.focus_force()

messagebox.showinfo("Message", text, parent=root)

root.destroy()

@app.post("/run")
def run():
    data = request.get_json(silent=True) or {}
    text = str(data.get("text", "No message"))

threading.Thread(target=show_popup, args=(text,), daemon=True).start()

return {"status": "ok"}

app.run("127.0.0.1", 5555)
```

Install Flask:

```bash
pip install flask
pip install flask-cors
```

Start the app:

```bash
python app.py
```

**JavaScript:**

```javascript
await fetch("http://127.0.0.1:5555/run", {
    method: "POST",
    headers: {
        "Content-Type": "application/json"
    },
    body: JSON.stringify({
        text: "Hello from JavaScript!"
    })
});
```

Or:

```javascript
body: JSON.stringify({
    text: "Your download has finished."
})
```

Or:

```javascript
body: JSON.stringify({
    command: "ping google.com"
});
```

This way, the Python application runs continuously in the background, and your JavaScript code can send commands to it at any time via `localhost`. It's a lightweight solution that requires very little code.