I have a Flask server like:

```
from flask import Flask
app = Flask(__name__, static_url_path='')

@app.route('/')
def server_index():
    return app.send_static_file('ngrok_run_a_public_server.html')

if __name__ == '__main__':
    app.run()

```

I have it in a folder like:

```
examples
  -ngrok_run_a_public_server.html
  -server.py

```

They are both in the same folder, and this is how I saw other people serve static files. I am getting `404` both locally and on ngrok. I just want to server a file publicly. 

It fails using both <http://127.0.0.1:5000/> and <http://127.0.0.1:5000>.