Daphne + Supervisor inside Docker Container can't access my application - nginx

Question

I'm trying to scale my Django app that uses Daphne server inside Docker container with Supervisor because Daphne has no workers. I read on the internet that it should be done that way but I didn't find any explanation of concept and the documentation is very obscure.
I managed to run it all inside container, logs are okay. I firstly run my app without supervisord with multiple containers and it worked fine. That is, I hosted multiple instance of same app in multiple containers because of redundancy. Then I read that I could run multiple processes of my app using supervisor inside container. So I managed to run app with supervisord and daphne inside container, I get logs that app is running, but I can't access it from my browser as I could when I had only one Daphne process per container without supervisord.
UPDATE:
I can even curl my application inside of container when I use curl localhost:8000, but I can't curl it by container's IP address nor inside, nor outside of the container. That means that it's not visible outside of container despite container's port being exposed in docker-compose file.
I'm getting
502 Bad Gateway
nginx/1.18.0
My supervisord config file looks like this:
[supervisord]
nodaemon=true
[supervisorctl]
[fcgi-program:asgi]
User=root
# TCP socket used by Nginx backend upstream
socket=tcp://localhost:8000
# Directory where your site's project files are located
directory=/app
# Each process needs to have a separate socket file, so we use process_num
# Make sure to update "mysite.asgi" to match your project name
command= /usr/local/bin/daphne -u /run/daphne/daphne%(process_num)d.sock --endpoint fd:fileno=0 --access-log - --proxy-headers WBT.asgi:application
# Number of processes to startup, roughly the number of CPUs you have
numprocs=4
# Give each process a unique name so they can be told apart
process_name=asgi%(process_num)d
# Automatically start and recover processes
autostart=true
autorestart=true
# Choose where you want your log to go
stdout_logfile=/home/appuser/supervisor_log.log
redirect_stderr=true
I can't see why NGINX throws 502 error.
This configuration worked until I introduced supervisor.
My Nginx is also inside its own docker container.
upstream django_daphne{
hash $remote_addr consistent;
server django_daphne_1:8000;
server django_daphne_2:8000;
server django_daphne_3:8000;
}
server {
server_name xxx.yyy.zzz.khmm;
listen 80;
client_max_body_size 64M;
location = /favicon.ico { access_log off; log_not_found off; }
location / {
proxy_pass http://django_daphne;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
#Websocket support
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}
location /api/ {
proxy_pass http://api_app:8888;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}

Answer 1

Okay! I found out what is a problem.
Instead of
socket=tcp://localhost:8000
it has to be
socket=tcp://0.0.0.0:8000
so that it can be accessed outside of the container.