Question 206047 in Docker Question posted in
The official documentation can be found here.

Docker cannot access service running at localhost from container in linux

I have service that is running at port 127.0.0.1:5433 in linux host machine, I want to access this service from the container using host.docker.internal but i could not.

version: "3"
services:
  streamlit:
    image: xxx/xxx
    build:
      context: .
      dockerfile: Dockerfile
      target: final
    ports:
      - "8501:8501"
    env_file:
      - .env
    entrypoint: scripts/app_entrypoint.sh
    volumes:
      - .:/app
    extra_hosts:
      - "host.docker.internal:host-gateway"

enter image description here

here is the output of ss -ltn which shows that 127.0.0.1:5433 is LISTENING, but when i try to access this port from inside the container, It says that port is closed. I doubt that this might be issues related to 127.0.0.1 and 0.0.0.0 so i started python http server on port 5433 and bind 0.0.0.0 then i was able to access it from inside the container, but when i start python http server and bind 127.0.0.1 instead i could not access from inside the container.

But i want to access service running on 127.0.0.1 from the container. My collegue on MAC is able to do so but I am using Linux machine and having this issue.

as you can see i have also used extra_hosts in my docker compose file as per documentation.

    extra_hosts:
      - "host.docker.internal:host-gateway"

Isn’t this sufficient to access service running on 127.0.0.1? and not only 0.0.0.0

Tags:

2

Answers


  1. 0

    Setting extra_hosts as host.docker.internal:host-gateway does not enable access to the host computer’s 127.0.0.1 (localhost) from within the Docker container.

    When you set extra_hosts as host.docker.internal:host-gateway, it enables the container to access the host’s network gateway. This allows the container to communicate with other devices on the local network or the internet. However, it does not grant access to the loopback address 127.0.0.1 on the host.

    The loopback address 127.0.0.1 is specific to each network namespace, and the container has its own separate network namespace from the host. Consequently, the container’s loopback address is distinct from the host’s loopback address. Therefore, setting extra_hosts does not provide direct access to the host’s 127.0.0.1.

    If you need to access services running on the host’s 127.0.0.1, you would typically use port mapping when running the container. By mapping the host’s port to a specific port on the container, you can access the services running on the host. For example:

    docker run -p 8080:8080 my-container

    With this configuration, you can access the service running on 127.0.0.1:8080 on the host by using localhost:8080 within the container.

    To further understand more about loopback address, check out the following:

    Login or Signup to reply.
  2. 0

    I am not pretty sure, But I guess you’ve misunderstood 0.0.0.0 and 127.0.0.1 so here is a small clarification.

    127.0.0.1 is a special IP address that is used to refer to the loopback network interface of the local machine, it will only accept connections from processes running on the same machine.

    while on the other hand, 0.0.0.0 is used to refer to all available network interfaces on the local machine. When you run a server process on your local machine and bind it to 0.0.0.0, it will accept connections from any IP address.

    and here is what you have done wrong, if you type in your terminal docker network inspect bridge you can check what is the IP that docker network is using. And I Think and am not sure that its 172.17.0.0/16 by default.

    You can check you container IP with this command, and you can access it throw the external port docker inspect --format '{{ .NetworkSettings.Networks.bridge.IPAddress }}' my-container

    if you want to communicate with the container from another container , you can use {container_name}:{internal_port} as from your example this will be streamlit:8501

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search