Docker / Networking, Ports & Service Connectivity
Check Docker's actual host-to-container port mapping
A container can listen internally without publishing a host port, or publish a different port than the caller expects. Inspect the mapping.
Environment and inputs: Docker Engine · Compose v2 and Buildx where specified; Linux containers unless noted. Verify daemon context, installed feature support and authorized host or Swarm manager access first.
Start with this check
Confirm the environment and replace sample objects, namespaces, images, paths and hosts with approved targets. Share only relevant, sanitized output. Follow the workload owner’s process for changes.
docker container port appRead the result
The command reports published bindings for the selected container. EXPOSE metadata alone does not create these bindings or prove the application listens.
Resolve and verify
Compare the client destination, host binding address and backend port with the deployment design. Correct the reviewed publication and verify the intended client path.
Before changing production
Do not publish an administrative port on every host interface just to make a local test succeed.