SQLSTATE[HY000] [2002] Connection refused error with laravel in docker - mysql

Question

it's my first time using docker so sorry if I'm making dumb mistakes. I'm trying to setup a docker container for laravel development. These are my files:
Dockerfile:
FROM php:8-fpm
COPY . /app
WORKDIR /app
COPY composer.lock composer.json ./
RUN apt-get update -y && apt-get install -y sendmail libpng-dev
RUN apt-get update && apt-get install -y \
build-essential \
curl
RUN curl -sSL https://github.com/mlocati/docker-php-extension-installer/releases/latest/download/install-php-extensions -o - | sh -s \
gd \
zip
RUN docker-php-ext-install mysqli pdo pdo_mysql
RUN curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
RUN composer update
RUN composer install
docker-compose.yaml:
version: '3.9'
name: caas-portal
services:
front:
build:
context: ./webapp
target: builder
ports:
- 4200:4200
volumes:
- ./webapp:/project
- /project/node_modules
mysql:
container_name: mysql
image: mysql:latest
environment:
- MYSQL_ROOT_PASSWORD=password
- MYSQL_DATABASE=db
ports:
- 3307:3306/tcp
networks:
- laravel
elasticsearch:
container_name: elasticsearch
image: docker.elastic.co/elasticsearch/elasticsearch:7.17.7
environment:
- discovery.type=single-node
ports:
- 9200:9200/tcp
- 9300:9300/tcp
volumes:
- 'elasticsearch:/usr/share/elasticsearch/data'
networks:
- laravel
app:
container_name: back
build: .
ports:
- 8000:80
networks:
- laravel
networks:
laravel:
driver: bridge
volumes:
elasticsearch:
driver: local
And this is the relevant part of my .env:
DB_CONNECTION=mysql
DB_HOST=mysql
DB_PORT=3307
DB_DATABASE=db
DB_USERNAME=root
DB_PASSWORD=password
When I run docker exec -it <container> sh and inside shell I run php artisan migrate I get the following error:
SQLSTATE[HY000] [2002] Connection refused (SQL: select * from information_schema.tables where table_schema = db and table_name = migrations and table_type = 'BASE TABLE')
I've seen similar posts, and tried to follow the answers given but still no luck. Where is the mistake, and how can it be corrected?

Answer 1

In your .env, try DB_PORT=3306.
According to Docker on Networking in Compose,
It is important to note the distinction between HOST_PORT and CONTAINER_PORT. [...] Networked service-to-service communication uses the CONTAINER_PORT.
If we apply this concept to your docker-compose.yaml, we know that the mysql service has a host port of 3307 while having a container port 3306.
Now if you want a your app service to connect to your mysql service (service-to-service communication), then within your app container you should connect using the mysql container port 3306, not 3307.