How to Access Host Port from Docker Container

TLDR

To access a host port from a Docker container, use the host.docker.internal hostname on macOS/Windows or the host's IP address on Linux. Configure the container's network mode if needed.

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Sometimes, you need a Docker container to communicate with a service running on the host machine. This guide explains how to access host ports from containers across different platforms.

Why Access Host Ports?

• Local Development: Test containerized apps with services running on the host.
• Debugging: Connect to host-based tools or databases.
• Integration: Bridge containerized and non-containerized services.

macOS and Windows: Use host.docker.internal

On macOS and Windows, Docker provides a special hostname, host.docker.internal, that resolves to the host machine's IP address.

Example:

# Access a service on host port 8080
curl http://host.docker.internal:8080

This works out of the box for most setups.

Linux: Use the Host's IP Address

On Linux, host.docker.internal is not available by default. Instead, use the host's IP address. To find it:

# Get the host's IP address
ip addr show docker0

Look for the inet field. For example, if the IP is 172.17.0.1, use it in your container:

curl http://172.17.0.1:8080

Using Host Network Mode

For direct access to host ports, run the container in --network host mode:

docker run --rm --network host nginx:alpine

In this mode, the container shares the host's network namespace, so it can access all host ports directly. Note that this mode is not recommended for production due to security concerns.

Visualizing the Connection

+-------------------+
| Host Machine |
+-------------------+
^
|
+-------------------+
| Docker Container |
+-------------------+

Best Practices

• Use host.docker.internal for simplicity on macOS/Windows.
• Avoid --network host in production unless absolutely necessary.
• Document host-port dependencies in your project.

By following these steps, you can enable seamless communication between Docker containers and host services.

Good luck with your project!