A beginner-friendly guide to Docker networking Why This Matters When you run an application in Docker, it doesn't automatically know how to reach other services. A container is isolated by default — it has its own network namespace, its own IP address, and its own view of the world. For two services to talk, you have to explicitly connect them. We would be exploring possible scenarios for communication among containers. This is something I learned while building SwiftDeploy . My Go API and Nginx were in separate containers and I didn't have full understanding of ow they communicated with each other. Scenario 1: Two Containers Talking to Each Other This is the most common scenario — an API and a database, or a frontend and a backend. The wrong way is to use localhost . If your API tries to connect to localhost:5432 for PostgreSQL, it won't work. Inside a container, localhost refers to the container itself — not your host machine, not another container. The right way is to use a Docker network.…