Docker Networking – Connecting Containers Like a Pro

1. Introduction

Docker networking allows containers to communicate with each other and the outside world.

Think of it like Wi-Fi for containers 📡—it enables seamless communication between services running in different containers.

In this guide, you'll learn how Docker networking works, how to expose ports, and how to connect multiple containers using a custom network. 🚀

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2. Basics of Docker Networking

Docker provides different networking options:

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3. Default Docker Bridge Network

By default, Docker containers run on the bridge network, allowing communication between containers on the same host.

Example: Running a Container on the Default Network

docker run -d --name mynginx nginx

Now, inspect the network:

docker network inspect bridge

✅ You’ll see that the container is connected to the default bridge network.

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4. How to Expose Ports & Access Containers from the Host

By default, containers cannot be accessed from the host unless ports are exposed.

Exposing a Port

docker run -d -p 8080:80 nginx

Now, open http://localhost:8080 in your browser to access the container. 🎉

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5. Creating and Using Custom Networks

For better container-to-container communication, create a custom network.

Step 1: Create a Network

docker network create mynetwork

Step 2: Run Containers on This Network

docker run -d --name webserver --network mynetwork nginx
docker run -d --name appserver --network mynetwork busybox sleep 3600

Step 3: Verify the Network

docker network inspect mynetwork

✅ Both containers can now communicate using their container names instead of IP addresses.

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6. Connecting Multiple Containers Using a Docker Network

Let’s connect a web app container to a database container using a Docker network.

Step 1: Create a Network

docker network create myappnetwork

Step 2: Run a Database Container

docker run -d --name mydb --network myappnetwork -e MYSQL_ROOT_PASSWORD=root mysql

Step 3: Run a Web App Container

docker run -d --name myapp --network myappnetwork my-web-app

Step 4: Access the Database from the App

Inside the myapp container, connect to mydb using:

mysql -h mydb -u root -p

✅ The app can now communicate with the database securely inside the network! 🎉

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7. Conclusion

Docker networking allows seamless container-to-container communication. Now you know how to:
✅ Use the default bridge network
✅ Expose ports to access containers
✅ Create and connect containers on custom networks

Try setting up a multi-container network today! 🚀