Docker container connection refused

[stevenh]

Inspector Version

• 0.16.8

Describe the bug
When using the published docker command from the readme connecting to the container doesn't work.

To Reproduce
Steps to reproduce the behavior:

1. Run the docker container

docker run --rm --network host -p 6274:6274 -p 6277:6277 ghcr.io/modelcontextprotocol/inspector:latest

2. Try to connect

curl http://localhost:6274

3. Connection fails:

curl: (7) Failed to connect to localhost port 6274 after 0 ms: Couldn't connect to server

Same happens if you click the link to load in a browser.

This site can’t be reached
localhost refused to connect.
Try:

Checking the connection
[Checking the proxy and the firewall](chrome-error://chromewebdata/#buttons)
ERR_CONNECTION_REFUSED

Expected behavior
A clear and concise description of what you expected to happen.
The browser should connect.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• OS: MacOS 26.0 (kernel: 25.0.0)
• Browser: Chrome Version 140.0.7339.208 (Official Build) (arm64) and curl

Additional context
Also tried without host networking enabled.

Also CTRL+C doesn't correctly stop the container either.

docker info
Client:
 Version:    28.4.0
 Context:    desktop-linux
 Debug Mode: false
 Plugins:
  ai: Docker AI Agent - Ask Gordon (Docker Inc.)
    Version:  v1.9.11
    Path:     /Users/steve/.docker/cli-plugins/docker-ai
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.28.0-desktop.1
    Path:     /Users/steve/.docker/cli-plugins/docker-buildx
  cloud: Docker Cloud (Docker Inc.)
    Version:  v0.4.27
    Path:     /Users/steve/.docker/cli-plugins/docker-cloud
  compose: Docker Compose (Docker Inc.)
    Version:  v2.39.2-desktop.1
    Path:     /Users/steve/.docker/cli-plugins/docker-compose
  debug: Get a shell into any image or container (Docker Inc.)
    Version:  0.0.42
    Path:     /Users/steve/.docker/cli-plugins/docker-debug
  desktop: Docker Desktop commands (Docker Inc.)
    Version:  v0.2.0
    Path:     /Users/steve/.docker/cli-plugins/docker-desktop
  extension: Manages Docker extensions (Docker Inc.)
    Version:  v0.2.31
    Path:     /Users/steve/.docker/cli-plugins/docker-extension
  init: Creates Docker-related starter files for your project (Docker Inc.)
    Version:  v1.4.0
    Path:     /Users/steve/.docker/cli-plugins/docker-init
  mcp: Docker MCP Plugin (Docker Inc.)
    Version:  v0.18.0
    Path:     /Users/steve/.docker/cli-plugins/docker-mcp
  model: Docker Model Runner (Docker Inc.)
    Version:  v0.1.40
    Path:     /Users/steve/.docker/cli-plugins/docker-model
  offload: Docker Offload (Docker Inc.)
    Version:  v0.4.27
    Path:     /Users/steve/.docker/cli-plugins/docker-offload
  sbom: View the packaged-based Software Bill Of Materials (SBOM) for an image (Anchore Inc.)
    Version:  0.6.0
    Path:     /Users/steve/.docker/cli-plugins/docker-sbom
  scout: Docker Scout (Docker Inc.)
    Version:  v1.18.3
    Path:     /Users/steve/.docker/cli-plugins/docker-scout
WARNING: Plugin "/Users/steve/.docker/cli-plugins/docker-dev" is not valid: failed to fetch metadata: fork/exec /Users/steve/.docker/cli-plugins/docker-dev: no such file or directory

Server:
 Containers: 3
  Running: 0
  Paused: 0
  Stopped: 3
 Images: 33
 Server Version: 28.4.0
 Storage Driver: overlayfs
  driver-type: io.containerd.snapshotter.v1
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 CDI spec directories:
  /etc/cdi
  /var/run/cdi
 Discovered Devices:
  cdi: docker.com/gpu=webgpu
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 05044ec0a9a75232cad458027ca83437aae3f4da
 runc version: v1.2.5-0-g59923ef
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.10.14-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: aarch64
 CPUs: 11
 Total Memory: 11.67GiB
 Name: docker-desktop
 ID: a85f5bbd-f12a-40de-b03a-482b11704019
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 HTTP Proxy: http.docker.internal:3128
 HTTPS Proxy: http.docker.internal:3128
 No Proxy: hubproxy.docker.internal
 Labels:
  com.docker.desktop.address=unix:///Users/steve/Library/Containers/com.docker.docker/Data/docker-cli.sock
 Experimental: false
 Insecure Registries:
  hubproxy.docker.internal:5555
  ::1/128
  127.0.0.0/8
 Live Restore Enabled: false

Testing with a basic nginx container works as expected:

docker run --rm --name nginx-test -p 8080:80 nginx:alpine

curl http://localhost:8080
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
...

Looks like this is a IPv6 / host networking issues.

After enabling host networking on docker desktop -> Settings -> Resources -> Network -> Enable host networking (ticked) and restarting docker the default command works.

There must be something about how the server is being started that is causing the issue as running a simple node server also works as expected:

docker run --rm -it -p 8080:3000 node:24-slim sh -c   "npm install -g serve && echo 'hello world' > index.html && serve -p 3000"

[NielsKSchjoedt]

+1