Bits of .NET

🌐 Containers Talk to Each Other

Multiple containers need to communicate. Docker Compose networking makes it easy. Use service names as hostnames.

📝 Docker Compose Networking

version: '3.8'
services:
  web:
    build: .
    ports:
      - "8080:8080"
    environment:
      - DB_HOST=postgres
      - REDIS_HOST=redis

  postgres:
    image: postgres:15
    environment:
      POSTGRES_PASSWORD: secret

  redis:
    image: redis:alpine

# Inside web container:
# ping postgres → resolves to postgres container IP
# ping redis → resolves to redis container IP

🎯 Custom Networks

version: '3.8'
services:
  web:
    networks:
      - frontend
      - backend

  api:
    networks:
      - backend

  database:
    networks:
      - backend

  nginx:
    networks:
      - frontend

networks:
  frontend:
    driver: bridge
  backend:
    driver: bridge

# web can talk to nginx and api
# api can talk to web and database
# nginx can only talk to web
# database can only talk to api

💡 Commands

• docker-compose up (creates default network)
• docker-compose up -d (detached mode)
• docker network ls (list networks)
• docker network inspect (inspect network)
• Service names resolve to container IPs