Containers cannot reach each other · Knowledge & Memory Center

STEP 1 OF 5

Are both containers on the same user-defined network? docker network inspect <net>

Test from inside the caller

SHELL

1docker network inspect <net> -f '{{range .Containers}}{{.Name}} {{end}}'

2docker exec -it <caller> getent hosts db # does the name resolve?

3docker exec -it <caller> nc -zv db 5432 # is the port open?

4docker exec -it <caller> wget -qO- http://api:8080/health

5

6# Tools missing in the image? Borrow a debug container on the same network

7docker run --rm -it --network <net> nicolaka/netshoot

Attach the container: docker network connect <net> <container>, or put both services in the same Compose file / network
The default bridge network has no DNS by name; create a user-defined network
App binds to 127.0.0.1: set it to 0.0.0.0 (e.g. --host 0.0.0.0, server.address=0.0.0.0)
Calling the host from a container: use host.docker.internal (add --add-host=host.docker.internal:host-gateway on Linux)