How to stop flask app.run()?
CTRL+C is the right way to quit the app, I do not think that you can visit the url after CTRL+C. In my environment it works well. 
What is the terminal output after CTRL+C? Maybe you can add some details. 
You can try to visit the url by curl to test if browser cache or anything related with browser cause this problem.
I made a flask app following flask's tutorial. After python flaskApp.py, how can I stop the app? I pressed ctrl + c in the terminal but I can still access the app through the browser. I'm wondering how to stop the app? Thanks.
I even rebooted the vps. After the vps is restated, the app still is running!