Develop Reference

Connect to Flask Server from other devices on same network

Dear smart people of stackoverflow,
I know this question has been asked a lot here but none of the posted solutions have worked for me as of yet. Any help here would be much appreciated:
The Problem: Cannot connect to flask app server from other devices (PCs, mobiles) on the same network. (in other words: localhost works perfectly but I cannot connect from external device)
What I've Tried:
1) Setting app.run(host='0.0.0.0', port=5000, debug=True, threaded=True) in the app.py so that the server will listen on all available network interfaces.
2) Enabling TCP traffic for port 5000 in local network in Windows Defender Firewall (with inbound and outbound rules added)
3) Using my host PC's IPv4 address in the URL bar of my external device's browser in the following format: http://<host_ipaddress>:<port>/
4) Using my host PC's hostname in the URL bar of my external device's browser in the following format: http://<host_name>:<port>/
5) Running the app.py file from Windows Powershell and Python (.py) Executor
None of these solutions has worked so far, even after attempting to connect from a few different external devices. Thanks in advance for your help!

I solved the issue by changing my home network profile to private instead of public, which allows my PC to be discoverable. Completely overlooked that!
Hope this helps someone!

Here is the method which worked for me.
Find the ip address of system using ifconfig command
Replace the host ip in code with your ip
server.py:
from flask import Flask
app = Flask(__name__)
#app.route('/')
def about():
return 'It worked!'
if __name__ == '__main__':
app.run(host='192.168.43.81', port=5000, debug=True, threaded=False)
To run the program:
python3 server.py
I know it is late, but I believe it can help others.

Much depends on how you're running your app. From what you've written, I'm guessing that you have
if __name__ == '__main__':
app.run(host='0.0.0.0', port=5000, debug=True, threaded=True)
If that's not working, changes are good that you're using flask run to start things up. The problem here is that flask will import your application before looking for app in your application's namespace. The problem is that __name__ will then reflect the name of the base file, and not __main__, so app.run() never gets run.
If that's the case, try passing --host=0.0.0.0 as an argument.

If you are on windows go to your internet settings and change network profile from Public to private

I did a similar setup with my django project. Your PC network settings are probably all good, but your router ( at least for wlan) is blocking the traffic. I solved this by tampering with needed settings in router manager api, which can be found from 192.168.1.1 in your local network. You can check your device ip addresses etc.

Go to your wifi settings and change network profile from public to private.
If its already private click on configure firewall and security settings shown below which opens windows security
There disable the microsoft defender firewall for private connections.
This worked for me

How to Serve a Local App Using Waitress and Nginx

I have a dash(plotly) app set up using flask as the server and can serve it on our Windows Server to port:8041 using waitress. My code to launch waitress is below;
#!/usr/bin/env python3
from waitress import serve
from src.pacedash.app import server as application
if __name__ == "__main__":
serve(application, threads=100, port=8041)
Everything works great if I use python run_waitress.py, except that when someone on our network navigates to the servename:8041 there is a "Not Secure" warning next to the url. Our IT vendor was able to get a cert file and key, but I'm not sure how to bring those into my current setup.
I have been trying to use nginx, but I can't find a guide to setting it up with waitress and I'm not too familiar with web apps or wsgi because I primarily work as the lone data person here.

I have been working on this same issue and have a solution. The nginx .conf file needs have a location defined like this:
location /myapp/ {
# Define the location of the proxy server to send the request to
proxy_pass http://localhost:8041/myapp/;
# standard proxy_set_header stuff below...
}
Then in your Dash application set the url_base_pathname to the same value:
app = dash.Dash(__name__, url_base_pathname='/myapp/')

I would use ngrok to expose your web app. It's amazingly simple:
Read this: https://ngrok.com/
I could be misinterpreting what you need, because I am not familiar with waitress (why not serve the app locally just using flask?), but if you need to test the live app, ngrok is what you should use.

flask with uwsgi nginx gateway timeout

I have set up a flask application to use uwsgi and nginx
I used the tutorials on the internet but I have the following issue
I have the following functions on the controller.py file
api_module = Blueprint('cassandra_api', __name__, url_prefix="/api")
#api_module.route('/', methods=['GET', 'POST'])
def home():
return "c"
the above works great when trying
myip/api/
but the following doesn't work at all
#api_module.route("/fault_prone_snippets/", methods=['GET'])
def get_fault_prone_snippets():
#code to connect with cassandra db and retrieve get parameters
When I visit
myip/api/faut_prone_snippets/
with or without get parameters, no code is executed, I don't see an error message and after the minute is over I get a gateway timeout. The problem is that when I run my flask from localhost it works great. Trying to use cassandra driver from the python console on my dev environment works too and connects with no error. How can I debug this kind of setup when it works locally but not in production?

As you're running behind nginx it might be that setting the keep_alive timeout in the http section of your nginx.conf will help. And/or proxy_send_timeout,
proxy_read_timeout parameters in the location section.

Problems with external visibility of Flask web-server

I have managed to to install flask and run the hello-world script:
from flask import Flask
app = Flask(__name__)
#app.route('/')
def hello_world():
return 'Hello World!'
if __name__ == '__main__':
app.run()
I was impressed how easy it was. Then I wanted to make my web-server visible externally. As recommended, I put host='0.0.0.0' as the argument of run function. Then I found my IP address (in Google) and put it in the address line of my web browser (while the hello-world-script was running).
As a result I got: "A username and password are being requested" and a dialogue box where I need to put a user name and password. I am not sure but I think it comes from my wireless network. Is there a way to change this behaviour?

How are you trying to run your application? If you run flask as app.run() - flask creates its own WSGI server on your host (by default 127.0.0.1) and port (by default 5000) (need permissions if port < 1000). If you run flask using nginx + WSGI or etc. your server resolves host and port.
Now it looks like you want get application by port which resolved your server like nginx or Apache. Try to get flask application by http://your-server-host-or-ip:5000 with the default port or try to change the port (set explicit) like app.run('0.0.0.0', 8080) and get it by http://your-server-host-or-ip:8080.
By the way, you can always get IP address using command-line tools e.g. ifconfig for Unix-like systems, or ipconfig /all for Windows.

To elaborate a little bit onto what #tbicr said, that password prompt indicates that you're trying to connect to your IP on port 80, which is most likely hosting an administration page for your router/modem. You want to connect to your IP on port 5000, the default port for Flask apps run with app.run().

How to declare ports in Cloud9 using Python

I'm new to using Cloud9 IDE (c9) and so far it looks great, except a few minor things.
I see from the docs that to start up a simple node.js http server, you have to pass in process.env.PORT in place of the regular port such as "8080".
Node Hello World example:
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello World\n');
}).listen(process.env.PORT, process.env.IP);
What I want to know is, on c9, can you only start services on ports using javascript / node.js? Or do other languages work just as well, perhaps with some other method of passing the port? Specifically python + Twisted?
I uploaded some twisted code that was working locally for me, but wouldn't work on c9 because it was trying to access local ports (which are already in use). Here is the error
twisted.internet.error.CannotListenError: Couldn't listen on any:8080: [Errno 98] Address already in use.
How would one make the following example work, if even possible, running on c9?
Python+Twisted Hello World example
from twisted.web import server, resource
from twisted.internet import reactor
class Simple(resource.Resource):
isLeaf = True
def render_GET(self, request):
return "<html>Hello, world!</html>"
site = server.Site(Simple())
reactor.listenTCP(8080, site)
reactor.run()
Initial searches through the documentation and github issues did not turn much up. I'm hoping this is possible and I just missed the right parameter to pass.
Edit: Updated output below
Node Code
console.log(process.env.PORT)
console.log(process.env.IP)
Terminal output
Running Node Process
Tip: you can access long running processes, like a server, at 'http://private-cloud.mrchampe.c9.io'.
Important: in your scripts, use 'process.env.PORT' as port and 'process.env.IP' as host.
8080
127.6.70.129
Python Code
import os
print os.environ["PORT"]
print os.environ["IP"]
Terminal output
Running Python Process
8080
127.6.70.129
Twisted code
import os
import twisted
from twisted.web import server, resource
from twisted.internet import reactor
class Simple(resource.Resource):
isLeaf = True
def render_GET(self, request):
return "<html>Hello, world!</html>"
site = server.Site(Simple())
reactor.listenTCP(int(os.environ["PORT"]), interface=os.environ["IP"])
reactor.run()
Terminal Output
Running Python Process
hello world
Traceback (most recent call last):
File "python/hello.py", line 17, in <module>
reactor.listenTCP(int(os.environ["PORT"]), interface=os.environ["IP"])
TypeError: listenTCP() takes at least 3 non-keyword arguments (2 given)
The listenTCP TypeError is strange because 2 arguments works locally but not on Cloud9. I don't see why using these arguments does not work.
I have the above code hosted on this public Cloud9 project for anyone to take a look. Thanks!

process.env.PORT and process.env.IP from Node.js sound like os.environ["PORT"] and os.environ["IP"] in Python. Perhaps you can try:
reactor.listenTCP(int(os.environ["PORT"]), site, interface=os.environ["IP"])

Probably this is limitation of c9 environment management, so users dont abuse their service too much. I would assume that they have some level of management for Node.js used resources and thus allow these to open ports.
If this was the case and I had to work with cloud9, I would probably approach this as follows:
- create Node.js service which would act as a proxy, listening on twisted behalf
- create new reactor with overriden listenTCP and listenUDP methods, which would bind these to Node.js proxy service.
The way how proxy would work is as follows, Node.js would initially listen on one "management" TCP port. Then, when twisted service starts up, it would create a TCP connection between Node.js and itself through that port. Then, whenever listenTCP or listenUDP is called, these commands would then be dispatched to Node.js service, which in return would open the port and all of the comunication through that port would then be proxied to twisted through that existing TCP connection.

It's worth mentioning that Jean-Paul's answer worked for me as well, but I had to use 'address' instead of 'interface':
http_server.listen(int(os.environ.get("PORT")), address=os.environ["IP"])