cannot communicate between docker container - connection refused

Question

I have a stack of n services defined in a docker compose file:

version: "3.7"
services:
  db:
    ...
  backend:
    image: $IMAGE_DEV_BACKEND
    container_name: "backend"
    hostname: backend
    ports:
      - "8888:8080"
    depends_on:
      - db
    networks:
      - backend
  frontend:
    image: $IMAGE_DEV_FRONTEND
    container_name: "frontend"
    hostname: frontend
    depends_on:
      - backend
    networks:
      - backend
      - traefik_default
volumes:
  data:
networks:
  backend:
    driver: bridge
    external:
      name: backend
  traefik_default:
    driver: bridge
    external:
      name: traefik_default

All container are in the same network.

In the frontend spring app I have a following spring configuration:

backend.url=http://backend:8888 when the frontend application tries to connect to the backend one I get

ERROR DefaultFormCommandBean:529 - Error while performing action "datastoreAction": I/O error on POST request for "http://backend:8888/oauth/token": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
org.springframework.web.client.ResourceAccessException: I/O error on POST request for "http://backend:8888/oauth/token": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:674)

when I use the IP address of the host with the docker daemon, everything works flawlessly, the containers can talk to each other.

What can I do to make it work with the container names?

Answer 1

Try using backend.url=http://backend:8080 . Port 8888 is used for accessing backend from your host machine, while 8080 is actual container's port. Check more information here .