How do I get Flask to run on port 80?

You don’t need to change port number for your application, just configure your www server (nginx or apache) to proxy queries to flask port. Pay attantion on uWSGI.

Your issue is, that you have an apache webserver already running that is already using port 80. So, you can either:

1. Kill apache: You should probably do this via /etc/init.d/apache2 stop, rather than simply killing them.

2. Deploy your flask app in your apache process, as flask in apache describes.

1- Stop other applications that are using port 80.
2- run application with port 80 :

if __name__ == '__main__':
      app.run(host='0.0.0.0', port=80)

For externally visible server, where you don’t use apache or other web server you just type

flask run --host=0.0.0.0 --port=80

I had to set FLASK_RUN_PORT in my environment to the specified port number. Next time you start your app, Flask will load that environment variable with the port number you selected.

If you use the following to change the port or host:

if __name__ == '__main__':
  app.run(host='0.0.0.0', port=80)

use the following code to start the server (my main entrance for flask is app.py):

python app.py

instead of using:

flask run

set the port with app.run(port=80,debug=True)
you should set debug to true when on dev

If you want your application on same port i.e port=5000 then just in your terminal run this command:

fuser -k 5000/tcp

and then run:

python app.py

If you want to run on a specified port, e.g. if you want to run on port=80, in your main file just mention this:

if __name__ == '__main__':  
    app.run(host='0.0.0.0', port=80)

Easiest and Best Solution

Save your .py file in a folder. This case my folder name is test. In the command prompt run the following

c:test> set FLASK_APP=application.py
c:test> set FLASK_RUN_PORT=8000
c:test> flask run

—————– Following will be returned —————-

 * Serving Flask app "application.py"
 * Environment: production
   WARNING: Do not use the development server in a production environment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://127.0.0.1:8000/ (Press CTRL+C to quit)
127.0.0.1 - - [23/Aug/2019 09:40:04] "[37mGET / HTTP/1.1[0m" 200 -
127.0.0.1 - - [23/Aug/2019 09:40:04] "[33mGET /favicon.ico HTTP/1.1[0m" 404 -

Now on your browser type: http://127.0.0.1:8000. Thanks

A convinient way is using the package python-dotenv:
It reads out a .flaskenv file where you can store environment variables for flask.

• pip install python-dotenv
• create a file .flaskenv in the root directory of your app

Inside the file you specify:

FLASK_APP=application.py
FLASK_RUN_HOST=localhost
FLASK_RUN_PORT=80

After that you just have to run your app with flask run and can access your app at that port.

Please note that FLASK_RUN_HOST defaults to 127.0.0.1 and FLASK_RUN_PORT defaults to 5000.

On my scenario the following steps worked like a charm:

• Installing the package:

  pip install --upgrade pip
  pip install python-dotenv
  

• Creating a hidden file in my app directory “flaskr/.flaskenv”

• Adding the following content:

  FLASK_APP=flaskr
  FLASK_RUN_HOST=localhost
  FLASK_RUN_PORT=8000
  

• Finally, run the flask command one more time:

  flask run
  

• The version which I am working on is:

  pip freeze |grep -i flask
  Flask==1.1.1
  

This is the only solution that worked for me on Ubuntu-18.

Inside the file app.py , use:

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=80)

The code above will give the same permission error unless sudo is used to run it:

sudo python3 app.py

you can easily disable any process running on port 80 and then run this command

flask run --host 0.0.0.0 --port 80

or if u prefer running it within the .py file

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=80)

I solved 2 times and solved it with 2 solution

The first solution, follow these steps:

1 open cmd

2 run ipconfig at cmd

3 copy IPv4 Address from cmd

4 Use your IPv4 as the local host in the next:

app.run(debug=True, port=5000, host='localhost')

at replace ‘localhost’ with your IPv4 Address

5 for your front end, do the same of step 4 like:

at ‘http://localhost:5000/auth’ replace ‘localhost’ with your IPv4 Address

Note: use the same port for {the frontend, and the backend}

6 run your both projects together(the backend and the frontend)

The second time, the last solution didn’t work, and I solved it with this:

• at the mobile side I used that URL: "http://10.0.2.2:8000" and at the Flask side used

app.run(debug=True, port=8000, host='localhost')