This content originally appeared on DEV Community and was authored by Yash Sonawane
🎬 "Ever wondered how your frontend talks to your backend inside Docker? Or how multiple containers magically connect like best friends at a tech meetup? In this episode, we dive into Docker networking — simply and visually."
🌐 Why Docker Networking Matters
In real-world apps, you don’t just run a single container.
You often run:
- A frontend (React, Vue, etc.)
- A backend (Node, Django, etc.)
- A database (MongoDB, Postgres, etc.)
These containers need to talk to each other, securely and efficiently.
Docker’s networking system makes this possible.
🔗 Types of Docker Networks
| Network Type | Use Case |
|---|---|
| Bridge | Default, isolated container networks |
| Host | Uses the host machine’s network directly |
| None | No network at all |
| Overlay | For multi-host Docker (Swarm, etc.) |
For most use cases (especially Docker Compose), Bridge is what you need.
🧪 Default Bridge Network
When you run containers without specifying a network:
docker run -d --name nginx nginx
Docker connects them to the bridge network. But by default, containers can’t talk to each other by name here.
You’d have to use IPs — not ideal. So let’s fix that.
🛠️ Create a Custom Bridge Network
docker network create my-network
Now, run containers and attach them:
docker run -d --name backend --network my-network my-backend-image
docker run -d --name frontend --network my-network my-frontend-image
✅ Now frontend can reach backend using its container name as hostname.
Example: http://backend:5000
🧪 Real Example: Node App + MongoDB
# Create custom network
docker network create dev-net
# Run MongoDB
docker run -d \
--name mongo \
--network dev-net \
mongo
# Run Node app connected to mongo
docker run -d \
--name app \
--network dev-net \
my-node-app
Inside my-node-app, you can now connect to Mongo using:
mongodb://mongo:27017
🔍 Inspecting Networks
List networks:
docker network ls
Inspect a network:
docker network inspect my-network
🚪 Port Mapping (Host ↔ Container)
Want to access your app in the browser?
docker run -d -p 8080:3000 my-app
This maps:
- Port 3000 inside the container
- To port 8080 on your machine
Visit: http://localhost:8080
🧠 Key Takeaways
- Use custom bridge networks to let containers talk by name
- Use
--networkwhen running multi-container apps - Inspect networks to understand connections
🔮 Up Next: Docker Compose — One YAML to Rule Them All
In Episode 8, we’ll cover:
- How to run multi-container apps with one command
- Docker Compose file structure
- Real-world project with frontend + backend + DB
💬 Over to You
Have you tried connecting containers via network yet?
Was the custom bridge easier than expected?
Comment below with your Docker networking wins or pain points!
❤️ If this episode made container networking click for you, share it with your dev buddy or team.
🎬 Next: “Docker Compose — Build Multi-Container Apps Like a Boss”
This content originally appeared on DEV Community and was authored by Yash Sonawane
Yash Sonawane | Sciencx (2025-08-29T03:09:00+00:00) 🛳️ Docker Series: Episode 7 — Docker Networking: How Containers Talk Behind the Scenes. Retrieved from https://www.scien.cx/2025/08/29/%f0%9f%9b%b3%ef%b8%8f-docker-series-episode-7-docker-networking-how-containers-talk-behind-the-scenes/
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