Combining internal and host-style networks

Docker Engine Compose
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1

Hello,
The compose file is as follows:

portal:
    container_name: portal
    restart: unless-stopped
    build:
      context: /home/docker/portal
      dockerfile: Dockerfile
    entrypoint: ["/usr/local/bin/entrypoint.sh"]
    command: ["php-fpm"]
    networks:
      app_network: {}
      host_network:
        aliases:
          - portal.host
    environment:
      APP_ENV: local
      DB_HOST: host.docker.internal
      DB_PORT: 3306
      DB_DATABASE: laravel
      DB_USERNAME: root
      DB_PASSWORD: 123456
      USER_ID: ${USER_ID:-999}
      GROUP_ID: ${GROUP_ID:-995}
    volumes:
      - /home/docker/portal:/var/www
    extra_hosts:
      - "host.docker.internal:host-gateway"

networks:
  app_network:
    driver: bridge
  host_network:
    external: true
    name: host_net

I want the portal container to simultaneously use the internal network to communicate with other containers and the external network to communicate with the host. The MariaDB is running on IP 0.0.0.0 and port 3306 on the host.
I logged into the portal container,
but I can’t see MariaDB on the host:

$ nc 172.20.2.58 -v 3306
Ncat: Version 7.93 ( https://nmap.org/ncat )
Ncat: No route to host.

You may blame me for doing this or find it strange, but I have to do this for a number of reasons.

Thank you.

2

Docker containers are for isolation. To be able to connect to a host service, you need to use the unique host IP (not localhost).

Or you add this line to Docker compose

services:
  xyz:
    extra_hosts:
      - host.docker.internal:host-gateway

and connect from inside Docker container via host.docker.internal.

3

Hello,
Thank you so much.
As you can see, I have used this line before, but the problem has not been resolved:

$ nc host.docker.internal -v 3306
Ncat: Version 7.93 ( https://nmap.org/ncat )
Ncat: No route to host.