Docker Flask App routing on windows system

Docker Desktop
1

Hello!

I’m trying to build a flask chat app but facing following issue (on windows)

sending post and get requests works fine locally through
127.0.0.1 - - [26/Oct/2024 16:54:56] “GET / HTTP/1.1” 200 -
127.0.0.1 - - [26/Oct/2024 16:55:17] “POST /send-message HTTP/1.1” 200 -

but as soon as the app is made into a docker container
the app opens through localhost:5000 and 127.0.0.1:5000 but port 172.17.0.1:5000 refuses to connect.
when request is run through localhost:5000 or 127.0.0.1:5000 the docker app automatically routes it through
172.17.0.1 - - [26/Oct/2024 16:54:56] “GET / HTTP/1.1” 200 -
172.17.0.1 - - [26/Oct/2024 16:55:17] “POST /send-message HTTP/1.1” 200 -
which does not get the response.

is there a way to get the 172.17.0.1 to connect or a way to route the post and get through 127.0.0.1 how to change the docker default

from
172.17.0.1 - - [26/Oct/2024 16:54:56] “GET / HTTP/1.1” 200 -

172.17.0.1 - - [26/Oct/2024 16:55:17] “POST /send-message HTTP/1.1” 200 -

Dockerfile

FROM python:3.10-slim

#container workdir
WORKDIR /app

#install chromium and dependencies
RUN apt-get update && apt-get install -y \
chromium \
chromium-driver \
libglib2.0-0 \
libnss3 \
libx11-xcb1 \
libxcomposite1 \
libxcursor1 \
libxdamage1 \
libxext6 \
libxfixes3 \
libxi6 \
libxrandr2 \
libxrender1 \
libdbus-glib-1-2 \
libatk1.0-0 \
libatk-bridge2.0-0 \
libfontconfig1 \
libx11-6 \
libx11-xcb-dev \
libxcb1 \
libxss1 \
fonts-liberation \
libappindicator3-1 \
xdg-utils \
wget \
unzip \
&& rm -rf /var/lib/apt/lists/*

RUN chmod +x /usr/bin/chromium && chmod +x /usr/bin/chromedriver

#copy dir contents to container
COPY . /app

#install packages
#RUN pip install -r requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

#expose app port

ENV HOST=0.0.0.0
ENV LISTEN_PORT 5000
EXPOSE 5000

#headless
ENV CHROME_BIN=/usr/bin/chromium
ENV CHROMEDRIVER_PATH=/usr/bin/chromedriver

#run
ENV FLASK_APP=app_local_new.py
ENV FLASK_ENV=production

#tested commands
CMD ["gunicorn", "-b", "0.0.0.0:5000", "app_local_new:app"]
#CMD ["gunicorn", "-w", "4", "-b", "0.0.0.0:5000", "--preload", "app_local_new:app"]
#CMD gunicorn -b 0.0.0.0:${PORT:-5000} "app_local_new:app"

docker-compose.yml

version: "3"
services:
app_local_new:
build: .
ports:
- "5000:5000"
networks:
- app-networks

networks:
app-networks:
driver: bridge

app_local_new.py

@app.route('/send-message', methods=['POST'])
def send_message():
data = request.get_json()
user_message = data.get('userMessage', '')
print(user_message)
2

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1 Like
3

The indentation of your code is still wrong. But regarding the IP address, since the container is in a virtual machine, you can’t access the container IP. I wrote about Dcoker networking here

https://dev.to/rimelek/docker-network-and-network-namespaces-in-practice-5h9#running-a-web-browser-in-a-net-namespace-in-a-vm-docker-desktop

and I refer to it on other pages of the original source of that tutorial too

Note

Since Docker Desktop runs containers in a virtual machine, Container IP addresses are not available from the host. You can run curl in a container on host network:

docker run --rm -it --net host curlimages/curl $IP:8080
1 Like
4

Hello, thanks for the materials. Read them and tried a few methods .

when running the app with:

docker run -d -p 5000:5000 flask-app

the app runs. Then after running

docker run --rm -it --net host curlimages/curl http://172.17.0.2:5000

the terminal returns the full site html from index.html. when curling

winpty docker run --rm -it --net host curlimages/curl -X POST http://172.17.0.1:5000/send-message -H "Content-Type: application/json" -d '{ "userMessage": "test message" }'

the site returns true as reply from the post.
docker terminal message:

2024-10-31 13:32:40 172.17.0.1 - - [31/Oct/2024 12:32:40] "POST /send-message HTTP/1.1" 200 -`Preformatted text`

however when running the script locally the app runs normally and post returns the answer

2024-10-31 13:32:40 127.0.0.1 - - [31/Oct/2024 12:32:40] "POST /send-message HTTP/1.1" 200 -
5

Besides the accidentally included “Preformatted text” string, I don’t see any difference. Of course the source IP could be different when you run it from different environments. I never used the experimental Docker Desktop terminal