I dont want to put every port used in docker-compose.yaml, but now I have to

Help
1

I have some basic experience with linux/docker/networking, and I am currently expanding my tiny homelab. Hugely grateful for any help in advance.

1. The problem I’m having:

I am trying to complete first configuration of Caddy, just “Hello, world!” from “Getting Started” documentaion for now, before I go into reverse-proxying all my other containers. After some troubleshooting after setting up, I managed to find that in order to set up ports in config, I need to add those in docker-compose.yaml, otherwise the connection is refused.

2. Error messages and/or full log output:

kaktus@raspi:/opt/docker/caddy $ curl http://raspi.kaktusland.xyz:2015/
curl: (7) Failed to connect to raspi.kaktusland.xyz port 2015 after 3 ms: Couldn't connect to server

3. Caddy version:

v2.11.2 h1:iOlpsSiSKqEW+SIXrcZsZ/NO74SzB/ycqqvAIEfIm64=

4. How I installed and ran Caddy:

a. System environment:

HW: Raspberry Pi 5 Model B Rev 1.0
OS: Debian GNU/Linux 12 (bookworm)
Kernel: 6.12.62+rpt-rpi-2712
Docker compose: v5.1.3

b. Command:

docker compose up -d

c. Service/unit/compose file:

services:
  caddy:
    container_name: caddy
    image: caddy:latest
    restart: unless-stopped
    cap_add:
      - NET_ADMIN
    ports:
      - "80:80"
      - "443:443"
      - "443:443/udp"
    volumes:
      - ./conf:/etc/caddy
      - ./site:/srv
      - caddy_data:/data
      - caddy_config:/config

volumes:
  caddy_data:
  caddy_config:

d. My complete Caddy config:

:2015

respond "Hello, world!"

5. What i tried:

After adding port used to docker-compose.yaml so it looks like this:

services:
  caddy:
    container_name: caddy
    image: caddy:latest
    restart: unless-stopped
    cap_add:
      - NET_ADMIN
    ports:
      - "2015:2015"
      - "80:80"
      - "443:443"
      - "443:443/udp"
    volumes:
      - ./conf:/etc/caddy
      - ./site:/srv
      - caddy_data:/data
      - caddy_config:/config

volumes:
  caddy_data:
  caddy_config:

Works as expected:

kaktus@raspi:/opt/docker/caddy $ curl http://raspi.kaktusland.xyz:2015/
Hello, world!

This does not seem correct, and I suppose I need to change someting on OS level - but what? Or is it something else?

2

That’s expected behaviour with Docker. If your app inside the container listens on a specific port and you are using a bridge network, Docker needs to map that port from the container to the host.

I’m a bit confused by your description though. You mentioned that it works as expected, but also that it does not seem correct. Could you clarify what part feels wrong to you?

Also, is there a reason you configured Caddy to listen on port 2015 instead of the default ports?

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