From inside a Docker container, how can I consume an API that is on the machine's localhost?

First of all, please forgive me if any information is missing or if my question does not meet the standards required by the site. I have very basic knowledge of docker, linux and networking and I am lost.

I use Ubuntu version 20.2 and I have docker version 20.10.10.

I have a system (CakePHP) running in a docker container, and an API (LARAVEL) running on my machine's local host (outside of the docker container), and I need to consume that API on the system from inside the docker container.

This is the content of docker-compose.yml

version: '2'
services:
  server-c10-php56:
    build:
      context: .
      dockerfile: Dockerfile
    image: php-c10-56
    volumes:
      - /srv/:/srv/
      - /var/www/html/:/var/www/html/
    ports:
      - "9056:80"
      - "9443:443"
    networks:
      - net30
    container_name: "docker-php56"
networks:
  sdnet:
    driver: "bridge"
  net30:
    ipam:
      driver: default
      config:
        - subnet: 172.30.0.0/16

As I understand it, the system (CakePHP) is running inside this 172.30.0.0/16 subnet.
And the system (CakePHP) to connect to PostgreSQL, connects through IP 172.30.0.1 (I think it's the gateway to access the local host of my machine).

The API I can consume normally by Postman.
Here is a screenshot of a test.

And on the system (CakePHP) from inside the docker container, I'm trying to consume like this (just testing for now).

It takes a while trying to connect, but without success. This is the return obtained ( sorry for the array format).

```
Array
(
[response] =>
[info] => Array
(
[url] => http://172.30.0.1:8000/api/queue/integracaoEcommerce
[content_type] =>
[http_code] => 0
[header_size] => 0
[request_size] => 0
[filetime] => -1
[ssl_verify_result] => 0
[redirect_count] => 0
[total_time] => 130.124754
[namelookup_time] => 1.8E-5
[connect_time] => 0

I'm not sure I can help you, but this might :

https://stackoverflow.com/questions/24319662/from-inside-of-a-docker-container-how-do-i-connect-to-the-localhost-of-the-mach

tldr (bridge mode):

to get the ip of the container (in container CLI) :
ip addr show eth0

to get the ip of the host's docker interface (host CLI) :
sudo ip addr show docker0

StackExchange DevOps Q#15140, answer score: 4