Configure Flask dev server to be visible across the network

Question

I m not sure if this is Flask specific  but when I run an app in dev mode  http   localhost 5000   I cannot access it from other machines on the network  with http    dev-host-ip  5000   With Rails in dev mode  for example  it works fine  I couldn t find any docs regarding the Flask dev server configuration  Any idea what should be configured to enable this

User · Answer

This answer is not solely related with flask, but should be applicable for all cannot connect service from another host issue.

use netstat -ano | grep <port> to see if the address is 0.0.0.0 or ::. If it is 127.0.0.1 then it is only for the local requests.
use tcpdump to see if any packet is missing. If it shows obvious imbalance, check routing rules by iptables.

Today I run my flask app as usual, but I noticed it cannot connect from other server. Then I run netstat -ano | grep <port>, and the local address is :: or 0.0.0.0 (I tried both, and I know 127.0.0.1 only allows connection from the local host). Then I used telnet host port, the result is like connect to .... This is very odd. Then I thought I would better check it with tcpdump -i any port <port> -w w.pcap. And I noticed it is all like this:

Then by checking iptables --list OUTPUT section, I could see several rules:

these rules forbid output tcp vital packets in handshaking. By deleting them, the problem is gone.

User · Answer

If none of the above solutions are working  try manually adding  quot http    quot  to the beginning of the url  Chrome can distinguish  quot  ip-address  5000 quot  from a search query   But sometimes that works for a while  and then stops connecting  seemingly without me changing anything   My hypothesis is that the browser might sometimes automatically prepend https     which it shouldn t  but this fixed it in my case

User · Answer

If your cool app has it s configuration loaded from an external file  like in the following example  then don t forget to update the corresponding config file with HOST  0 0 0 0   cool app run      host cool app config get  HOST    localhost        port cool app config get  PORT   9000

User · Answer

Check whether the particular port is open on the server to serve the client or not    in Ubuntu or Linux distro  sudo ufw enable sudo ufw allow 5000 tcp   allow the server to handle the request on port 5000   Configure the application to handle remote requests  app run host  0 0 0 0    port 5000    python3 app py  amp   run application in background

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Go to your project path on CMD command Prompt  and execute the following command -  set FLASK APP ABC py  SET FLASK ENV development  flask run -h  yourIP  -p 8080  you will get following o p on CMD -   Serving Flask app  expirement py   lazy loading    Environment  development Debug mode  on Restarting with stat Debugger is active  Debugger PIN  199-519-700 Running on http    yourIP  8080   Press CTRL C to quit     Now you can access your flask app on another machine using http    yourIP  8080  url

User · Answer

For me  i followed the above answer and modified it a bit    Just grab your ipv4 address using ipconfig on command prompt Go to the file in which flask code is present In main function write app run host   your ipv4 address     Eg

User · Answer

Create file  flaskenv in the project root directory    The parameters in this file are typically   FLASK APP app py FLASK ENV development FLASK RUN HOST  dev-host-ip  FLASK RUN PORT 5000   If you have a virtual environment  activate it and do a pip install python-dotenv    This package is going to use the  flaskenv file  and declarations inside it will be automatically imported across terminal sessions   Then you can do flask run

User · Answer

If you use the flask executable to start your server  you can use flask run --host 0 0 0 0 to change the default from 127 0 0 1 and open it up to non local connections  The config and app run methods that the other answers describe are probably better practice but this can be handy as well      Externally Visible Server If you run the server you will notice that   the server is only accessible from your own computer  not from any   other in the network  This is the default because in debugging mode a   user of the application can execute arbitrary Python code on your   computer       If you have the debugger disabled or trust the users on your network    you can make the server publicly available simply by adding   --host 0 0 0 0 to the command line       flask run --host 0 0 0 0 This tells your operating system to listen on   all public IPs    Reference  http   flask pocoo org docs 0 11 quickstart

User · Answer

While this is possible  you should not use the Flask dev server in production  The Flask dev server is not designed to be particularly secure  stable  or efficient  See the docs on deploying for correct solutions   Add a parameter to your app run     By default it runs on localhost  change it to app run host   0 0 0 0   to run on all your machine s IP addresses  0 0 0 0 is a special value  you ll need to navigate to the actual IP address  Documented on the Flask site under  quot Externally Visible Server quot  on the Quickstart page   Externally Visible Server If you run the server you will notice that the server is only available from your own computer  not from any other in the network  This is the default because in debugging mode a user of the application can execute arbitrary Python code on your computer  If you have debug disabled or trust the users on your network  you can make the server publicly available  Just change the call of the run   method to look like this  app run host  0 0 0 0   This tells your operating system to listen on a public IP

User · Answer

You can also set the host  to expose it on a network facing IP address  and port via environment variables    export FLASK APP app py   export FLASK ENV development   export FLASK RUN PORT 8000   export FLASK RUN HOST 0 0 0 0    flask run    Serving Flask app  quot app py quot   lazy loading     Environment  development    Debug mode  on    Running on https   0 0 0 0 8000   Press CTRL C to quit     Restarting with stat    Debugger is active     Debugger PIN  329-665-000  See How to get all available Command Options to set environment variables

User · Answer

go to project path     set FLASK APP ABC py     SET FLASK ENV development  flask run -h  yourIP  -p 8080 you will following o p on CMD -   Serving Flask app  expirement py   lazy loading     Environment  development    Debug mode  on    Restarting with stat    Debugger is active     Debugger PIN  199-519-700    Running on http    yourIP  8080   Press CTRL C to quit

User · Answer

Add below lines to your project  if   name         main         app debug   True     app run host    0 0 0 0  port 5005

User · Answer

I had the same problem  I use PyCharm as an editor and when I created the project  PyCharm created a Flask Server  What I did was create a server with Python in the following way    basically what I did was create a new server but flask if not python  I hope it helps you

User · Answer

If you re having troubles accessing your Flask server  deployed using PyCharm  take the following into account    PyCharm doesn t run your main  py file directly  so any code in if   name         main     won t be executed  and any changes  like app run host  0 0 0 0   port 5000   won t take effect   Instead  you should configure the Flask server using Run Configurations  in particular  placing --host 0 0 0 0 --port 5000 into Additional options field      More about configuring Flask server in PyCharm

User · Answer

Try this if the 0 0 0 0 method doesn t work Boring Stuff I personally battled a lot to get my app accessible to other devices laptops and mobile phones  through a local-server  I tried the 0 0 0 0 method  but no luck  Then I tried changing the port  but it just didn t work  So  after trying a bunch of different combinations  I arrived to this one  and it solved my problem of deploying my app on a local server  Steps  Get the local IPv4 address of your computer  This can be done by typing ipconfig on Windows and ifconfig on Linux and Mac    Please note  The above step is to be performed on the machine you are serving the app on  and on not the machine on which you are accessing it  Also note  that the IPv4 address might change if you disconnect and reconnect to the network   Now  simply run the flask app with the acquired IPv4 address  flask run -h 192 168 X X E g  In my case  see the image   I ran it as  flask run -h 192 168 1 100    On my mobile device  Optional Stuff If you are performing this procedure on Windows and using Power Shell as the CLI  and you still aren t able to access the website  try a CTRL   C command in the shell that s running the app  Power Shell gets frozen up sometimes and it needs a pinch to revive  Doing this might even terminate the server  but it sometimes does the trick  That s it  Give a thumbs up if you found this helpful  Some more optional stuff I have created a short Powershell script that will get you your IP address whenever you need one   env getIp   ipconfig if   env getIp -match   IPv4  sa-zA-Z     s 0-9             if   matches 1  -match     a-z s   d     d                ipv4    matches 1          echo  ipv4  Save it to a file with  ps1 extension  for PowerShell   and run it on before starting your app  You can save it in your project folder and run it as    getIP ps1  flask run -h  ipv4  Note  I saved the above shellcode in getIP ps1  Cool

[python] Configure Flask dev server to be visible across the network

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