Networking (original) (raw)

Docker Desktop includes built-in networking capabilities to help you connect containers with services on your host, across containers, or through proxies and VPNs.

VPN Passthrough

Docker Desktop networking can work when attached to a VPN. To do this, Docker Desktop intercepts traffic from the containers and injects it into the host as if it originated from the Docker application.

Port mapping

When you run a container with the -p argument, for example:

Docker Desktop makes whatever is running on port 80 in the container, in this case, nginx, available on port 80 of localhost. In this example, the host and container ports are the same.

To avoid conflicts with services already using port 80 on the host:

Now connections to localhost:8000 are sent to port 80 in the container.

Tip

The syntax for -p is HOST_PORT:CLIENT_PORT.

HTTP/HTTPS Proxy support

SeeProxies

SOCKS5 proxy support

SOCKS (Socket Secure) is a protocol that facilitates the routing of network packets between a client and a server through a proxy server. It provides a way to enhance privacy, security, and network performance for users and applications.

You can enable SOCKS proxy support to allow outgoing requests, such as pulling images, and access Linux container backend IPs from the host.

To enable and set up SOCKS proxy support:

  1. Navigate to the Resources tab in Settings.
  2. From the dropdown menu select Proxies.
  3. Switch on the Manual proxy configuration toggle.
  4. In the Secure Web Server HTTPS box, paste your socks5://host:port URL.

SSH agent forwarding

Docker Desktop for Mac and Linux lets you use the host’s SSH agent inside a container. To do this:

  1. Bind mount the SSH agent socket by adding the following parameter to your docker run command:
  2. Add the SSH_AUTH_SOCK environment variable in your container:

To enable the SSH agent in Docker Compose, add the following flags to your service:

Changing internal IP addresses

The internal IP addresses used by Docker can be changed from Settings. After changing IPs, you need to reset the Kubernetes cluster and to leave any active Swarm.

There is no docker0 bridge on the host

Because of the way networking is implemented in Docker Desktop, you cannot see a docker0 interface on the host. This interface is actually within the virtual machine.

I cannot ping my containers

Docker Desktop can't route traffic to Linux containers. However if you're a Windows user, you can ping the Windows containers.

Per-container IP addressing is not possible

This is because the Docker bridge network is not reachable from the host. However if you are a Windows user, per-container IP addressing is possible with Windows containers.

I want to connect from a container to a service on the host

The host has a changing IP address, or none if you have no network access. Docker recommends you connect to the special DNS name host.docker.internal, which resolves to the internal IP address used by the host.

You can also reach the gateway using gateway.docker.internal.

If you have installed Python on your machine, use the following instructions as an example to connect from a container to a service on the host:

  1. Run the following command to start a simple HTTP server on port 8000.
    python -m http.server 8000
    If you have installed Python 2.x, run python -m SimpleHTTPServer 8000.
  2. Now, run a container, install curl, and try to connect to the host using the following commands:

I want to connect to a container from the host

Port forwarding works for localhost. --publish, -p, or -P all work. Ports exposed from Linux are forwarded to the host.

Docker recommends you publish a port, or to connect from another container. This is what you need to do even on Linux if the container is on an overlay network, not a bridge network, as these are not routed.

For example, to run an nginx webserver:

To clarify the syntax, the following two commands both publish container's port 80 to host's port 8000:

To publish all ports, use the -P flag. For example, the following command starts a container (in detached mode) and the -P flag publishes all exposed ports of the container to random ports on the host.

Alternatively, you can also usehost networkingto give the container direct access to the network stack of the host.

See therun command for more details on publish options used with docker run.