Docker
/Beginner
Port Mapping
Definition
The process of forwarding a specific port on the Host machine's physical network interface to a specific port inside the isolated Docker container.
Explain Like I'm New
Punching a hole in the wall. The container is completely isolated; nobody from the outside can reach it. Port mapping drills a hole through the host computer directly into the container so internet traffic can get in.
Real World Example
Running `docker run -p 8080:80 nginx`. The NGINX container is listening on port 80. The `-p 8080:80` tells the Host laptop: 'If anyone goes to `localhost:8080` in Chrome, immediately tunnel that traffic into the container's port 80.'
Common Use Cases
- •Exposing web apps
- •Allowing external database connections
Interview Questions
basic
- In the command `-p 3000:80`, which port is the one the user types into their web browser?
intermediate
- What happens if you run two containers and try to map them both to Host port 8080?