How networking works in Docker

Containers can communicate through Docker networks. A well-designed network isolates services and exposes only the ones you need.

1. Create a network

docker network create app_net

2. Connect containers

docker run -d --name db --network app_net mysql:8
docker run -d --name web --network app_net nginx

Now web can reach the database using the name db as a hostname, without exposing MySQL externally.

3. Isolation

Put the database on an internal network and the web server on a public one. Only the web server has access to both. That way MySQL is never directly reachable from the internet.

4. Useful commands

docker network ls
docker network inspect app_net
docker network connect app_net container

In Docker Compose

Compose automatically creates a network for the services in the file, so they reach each other by name. See Docker Compose.