How do I get Flask to run on port 80

Question

I have a Flask server running through port 5000  and it s fine  I can access it at http   example com 5000  But is it possible to simply access it at http   example com  I m assuming that means I have to change the port from 5000 to 80  But when I try that on Flask  I get this error message when I run it   Traceback  most recent call last     File  xxxxxx py   line 31  in  lt module gt  app run host  0 0 0 0   port int  80    debug True     File   usr local lib python2 6 dist-packages flask app py   line 772  in run run simple host  port  self    options    File   usr local lib python2 6 dist-packages werkzeug serving py   line 706  in run simple     test socket bind  hostname  port     File   lt string gt    line 1  in bind socket error   Errno 98  Address already in use   Running lsof -i  80 returns   COMMAND   PID     USER   FD   TYPE   DEVICE SIZE OFF NODE NAME apache2   467     root    3u  IPv4 92108840      0t0  TCP   www  LISTEN  apache2  4413 www-data    3u  IPv4 92108840      0t0  TCP   www  LISTEN  apache2 14346 www-data    3u  IPv4 92108840      0t0  TCP   www  LISTEN  apache2 14570 www-data    3u  IPv4 92108840      0t0  TCP   www  LISTEN  apache2 14571 www-data    3u  IPv4 92108840      0t0  TCP   www  LISTEN  apache2 14573 www-data    3u  IPv4 92108840      0t0  TCP   www  LISTEN    Do I need to kill these processes first  Is that safe  Or is there another way to keep Flask running on port 5000 but have the main website domain redirect somehow

User · Answer

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

User · Answer

Your issue is  that you have an apache webserver already running that is already using port 80  So  you can either    Kill apache  You should probably do this via  etc init d apache2 stop  rather than simply killing them  Deploy your flask app in your apache process  as flask in apache describes

User · Answer

So it s throwing up that error message because you have apache2 running on port 80   If this is for development  I would just leave it as it is on port 5000   If it s for production either   Not Recommended   Stop apache2 first     Not recommended as it states in the documentation      You can use the builtin server during development  but you should use a full deployment option for production applications   Do not use the builtin development server in production     Recommended   Proxy HTTP traffic through apache2 to Flask    This way  apache2 can handle all your static files  which it s very good at - much better than the debug server built into Flask  and act as a reverse proxy for your dynamic content  passing those requests to Flask   Here s a link to the official documentation about setting up Flask with Apache   mod wsgi   Edit 1 - Clarification for  Djack     Proxy HTTP traffic to Flask through apache2   When a request comes to the server on port 80  HTTP  or port 443  HTTPS  a web server like Apache or Nginx handles the connection of the request and works out what to do with it  In our case a request received should be configured to be passed through to Flask on the WSGI protocol and handled by the Python code  This is the  dynamic  part       reverse proxy for dynamic content   There are a few advantages to configuring your web server like the above     SSL Termination - The web server will be optimized to handle HTTPS requests with only a little configuration  Don t  roll your own  in Python which is probably very insecure in comparison  Security - Opening a port to the internet requires careful consideration of security  Flask s development server is not designed for this and could have open bugs or security issues in comparison to a web server designed for this purpose  Note that a badly configured web server can also be insecure   Static File Handling - It is possible for the builtin Flask web server to handle static files however this is not recommended  Nginx Apache are much more efficient at handling static files like images  CSS  Javascript files and will only pass  dynamic  requests  those where the content is often read from a database or the content changes  to be handled by the Python code    more  This is bordering on scope for this question  If you want more info do some research into this area

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

set the port with app run port 80 debug True  you should set debug to true when on dev

User · Answer

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

User · Answer

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

User · Answer

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       quot   main   quot       app run host 0 0 0 0  port 80

User · Answer

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 gt  set FLASK APP application py c  test gt  set FLASK RUN PORT 8000 c  test gt  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

User · Answer

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

User · Answer

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

User · Answer

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

[python] How do I get Flask to run on port 80?

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