[Python] Flask 'Cannot assign requested address' error when binding to a specific IP on...

I have Virtual Dedicated Server based on Ubuntu 20.04.6 with IP address 193.23.xxx.xx. blizcore.fun resolves to this IP. On this server I installed pterodactyl panel. Pterodactyl have IP 172.18.0.0/16. I install basic python 3.10 egg on pterodactyl and create server to port 6668.

My target: create GET request to https://blizcore.fun/status. This request should be handled by the Flask server running within the Pterodactyl environment.

Code:

from flask import Flask, request
from flask_restful import Api, Resource, abort

from dotenv import load_dotenv
load_dotenv()
import os

key = os.getenv("AUTH_KEY")

app = Flask(__name__)
api = Api()

class BlizcoreApi(Resource):
def get(self):
headers = request.headers
auth = headers.get("Authorization")
if auth == key:
return {"code": 200, "message": "All working stable."}
else:
return abort(401, message="Unauthorized.")


api.add_resource(BlizcoreApi, "/status")
api.init_app(app)

if __name__ == "__main__":
app.run(host="193.23.220.14", port=6668, debug=True)


But i have error (console output of server on port 6668):

* Serving Flask app 'server'
* Debug mode: on
Cannot assign requested address


I tried connect flask to host 0.0.0.0 for listen on all interfaces and Im connected to pterodactyl IP (console output after these actions):

* Serving Flask app 'server'
* Debug mode: on
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
* Running on all addresses (0.0.0.0)
* Running on http://127.0.0.1:6668
* Running on http://172.18.0.6:6668
Press CTRL+C to quit
* Restarting with stat
* Debugger is active!
* Debugger PIN: 144-915-975


Rules on Firewall looks like that:

root@vm25-lendnodes:~# sudo ufw status
Status: active

To Action From
-- ------ ----
22 ALLOW Anywhere
80 ALLOW Anywhere
443 ALLOW Anywhere
...
6668 ALLOW 172.18.0.0/24
...


I think I need to make a router to connect the stream from 172.18.0.6:6668 to 193.23.xxx.xx:6668, but it just my theory.

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