Rest name resolution not working

Configuration
1

I use the latest docker ( * Core 2025.4.0 * Frontend 20250401.0) but without network_mode: host, because homeassistant (http://homeassistant.dockerbox.local) and raspberrymatic (http://raspberrymatic.dockerbox.local/) run on the same host behind a traefic reverse proxy.
they are also in the same docker network.
If I connect to the homeassistant docker and run the rest call via curl (I have to escape & and ?) there it works, but not via the rest platform (even with escaping).

curl http://raspberrymatic.dockerbox.local/addons/xmlapi/state.cgi\?sid=my_token\&device_id=2679
<?xml version='1.0' encoding='ISO-8859-1' ?><state><device name='HM-ES-PMSw1-Pl-DN-R1 OEQ0572643' ise_id='2679' unreach='false' sticky_unreach='false' config_pending='false' ><channel name='HM-ES-PMSw1-Pl-DN-R1

the error is:

# container start
2025-04-04 21:09:28.161 DEBUG (MainThread) [homeassistant.components.rest.data] Updating from http://raspberrymatic.dockerbox.local/addons/xmlapi/state.cgi?sid=my_token&device_id=2679

2025-04-04 21:09:28.166 WARNING (MainThread) [homeassistant.components.sensor] Platform rest not ready yet: [Errno -2] Name does not resolve; Retrying in background in 30 seconds

2025-04-04 21:09:30.255 DEBUG (MainThread) [homeassistant.components.rest.data] Updating from http://raspberrymatic.dockerbox.local/addons/xmlapi/state.cgi?sid=my_token&device_id=2679

I don’t really understand why the name resolution works in the docker but not in the application in the docker.

my config is:

# Loads default set of integrations. Do not remove.
default_config:

# Load frontend themes from the themes folder
frontend:
  themes: !include_dir_merge_named themes

homeassistant:
  internal_url: "http://homeassistant.dockerbox.local"
  external_url: "http://homeassistant.dockerbox.local"

automation: !include automations.yaml
script: !include scripts.yaml
scene: !include scenes.yaml

logger:
  default: warning
  logs:
    homeassistant.components.rest: debug

http:
  use_x_forwarded_for: true
  trusted_proxies:
    - 172.18.0.0/16

sensor:
  - platform: rest
    name: "Smart Plug Power"
    resource: 'http://raspberrymatic.dockerbox.local/addons/xmlapi/state.cgi?sid=my_token&device_id=2679'
    scan_interval: 10
    verify_ssl: false
    value_template: >
      {% for state in value_json.state | selectattr('name', 'equalto', 'POWER') %} {{ state.value | float }} {% endfor %}
    unit_of_measurement: "W"
2

I searched for two hours and 5min after creating the post I found the solution…
maybe it’s interssting for somebody else:
you have to use the docker service name:

    resource: 'http://raspberrymatic/addons/xmlapi/state.cgi?sid=my_token&device_id=2679'