Inputs and Port Mapping
Inputs
By default, a Docker container does not listen to standard input and runs in a non-interactive shell. However, you can enable interactive input and terminal mapping by using specific flags:
-i: Runs the container in interactive mode, allowing it to receive input from the standard input (stdin).-t: Allocates a pseudo-TTY, mapping the terminal of the host to the container's terminal.
As an example, you can use a simple image of an app that prompts the user for input:
docker pull kodekloud/simple-prompt-docker
docker run -it kodekloud/simple-prompt-docker
Port Mapping
The underlying host where Docker is installed is referred to as the Docker Host or Docker Engine. To access applications running in a Docker container from a web browser, you can use the container's internal IP address, which is only accessible from the host itself.
Getting the Container IP Address
To retrieve the IP address of a running container:
docker ps
docker inspect <container-id>
To access the IP from within the host, you can open the IP address in a web browser or use curl in the host's terminal. For example, if the container is running on port 8080, you can test it with:
curl <ip-of-vm>:8080
Port Mapping to Access from Outside
To make your application accessible from outside the host, you need to map the internal container port to a port on the Docker host. This can be achieved using the -p flag.
Example: To map container port 5000 to host port 80, you would run:
docker run -d -p 80:8080 kodekloud/simple-webapp
Viewing Port Mappings
To see the current port mappings on your Linux machine, you can run:
netstat -tulpn
This command will display a list of all network connections and listening ports, helping you verify the mappings you've set up.