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.
 
     
     
    