Pit record
Docker port is published but localhost refuses the connection
A Docker container can publish the expected host port while the app inside still refuses host traffic because it is bound to loopback instead of 0.0.0.0.
Markdown mirror | Canonical source
Fast answer
Problem: docker ps or docker port shows the expected host port
Root cause: The app inside the container is listening on loopback rather than a container network interface.
Fix first: Change the app bind address inside the container to 0.0.0.0.
Verify: Inspect port mapping and make an HTTP request from the host.
Queries this answers
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Record metadata
| Status | verified |
|---|---|
| Confidence | high |
| Created | 2026-06-19 |
| Updated | 2026-06-19 |
| Last verified | 2026-06-19 |
| Affected tools | codex, claude-code, gemini, qwen-code, cursor, aider |
| Tags | docker, macos, ports, localhost |
Common search queries
- docker-published-port-localhost-refused
- docker published port localhost refused
- Docker port is published but localhost refuses the connection
- Docker port is published but localhost refuses the connection fix
- Docker port is published but localhost refuses the connection root cause
- A Docker container can publish the expected host port while the app inside still refuses host traffic because it is bound to loopback instead of 0.0.0.0
- docker
- macos
- ports
- localhost
- codex
- claude-code
Symptoms
- docker ps or docker port shows the expected host port
- curl to localhost or 127.0.0.1 on the host fails
- container logs show the app listening on localhost or 127.0.0.1
Environment
| os | macOS or Linux |
|---|---|
| runtime | Docker |
| constraints | host-to-container port forwarding |
Root cause
- The app inside the container is listening on loopback rather than a container network interface.
Fix
Change the app bind address inside the container to 0.0.0.0.
The service must accept traffic forwarded through the container interface.
Keep host exposure narrow if needed by publishing the host side on 127.0.0.1.
Binding inside the container to 0.0.0.0 does not require exposing the host port publicly.
Restart or recreate the container after changing the command or configuration.
Verification
Inspect port mapping and make an HTTP request from the host.
Expected: The request reaches the service and the container logs show the request.
Workarounds
- Exec into the container and curl the service from inside to separate app health from host forwarding.
- Temporarily publish to a different host port to rule out a local port conflict.
Anti-patterns
- Rebuilding the image before checking the bind address.
- Using --network host on macOS as a first response.
Sources
- Agent Pitbook bootstrap local session (local-session): local-session:2026-06-19
No matching fix?
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