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Yash Sonawane
Yash Sonawane

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🛳️ Docker Series: Episode 7 — Docker Networking: How Containers Talk Behind the Scenes

#docker #tutorial #productivity #beginners

🎬 "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
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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
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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
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✅ 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
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Inside my-node-app, you can now connect to Mongo using:

mongodb://mongo:27017
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🔍 Inspecting Networks

List networks: 

docker network ls
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Inspect a network: 

docker network inspect my-network
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🚪 Port Mapping (Host ↔ Container)

Want to access your app in the browser?

docker run -d -p 8080:3000 my-app
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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 --network when 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”

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