Encountered The requested URL was not found when studying flask on the server. If you entered the URL manually please check your spelling and try again this mistake, as our website is http://127.0.0.1:5000/
It is natural to think the port is not a problem, open a terminal and enter 
the emergence of information port is occupied by:
To see what is being occupied by the program: Enter 
through the pid number, look for the program,
Python.exe port is occupied, so we end the process: input taskkill / f / t / im python.exe 
At this point we will be able to run the program