#Docker container port mapping code#

So in this case, we're going to use a lowercase P flag, which is the short form of publish, and it allows you to specify the port on the host that you want to use, and then a colon, and then the port on the container. Now, you can also use the publish flag, which will allow you to map specific ports. So using publish all, you can dynamically map the ports that are exposed from the container to the host. And that's going to remove them both.Īll right, perfect. So now that they're stopped, let's prune them. And notice that the stop command allows you to pass in multiple container IDs. So it's going to map that for us automatically. So now if we start up another container, again using the publish all flag to dynamically map the ports, it's going to choose a different port automatically.Īnd notice the first container in the list here is 32769, and the second one is 32768. If I use the terminal-based browser Lynx, you can see that the site is up and running. So if we curl localhost on that port, we should get back some HTML. So we can use the docker ps command to see which port. It will also dynamically bind the exposed port 8080 to a port on the host. So this is going to run the container in detached mode, which means it's gonna run in the background. The minus capital P flag is the short form of publish all. Publish all will dynamically map the exposed ports of the container to open ports on the host. Docker lets you bind the container port to a host port with the publish or publish all flags. By default, the expose instruction really doesn't do anything to the host. The Docker file specifies that the container exposes port 8080. However, there is another way to interact with a web application inside of a container, and that would be to bind the port in the container to a port on the host.ĭocker allows you to do this dynamically or explicitly. So this is the home page of the app.īecause each container has its own IP address, all of them can run on port 8080 inside of their own container, and then we can interact with them via their IP address.

And if we curl this and we use port 8080, you can see that we get back some HTML. Notice here, the IP address field, you can see that it's set with the container's IP. It's possible to fetch the IP address using the docker inspect command and then passing in the container ID or name. So for now, the thing to know is that this web app is running inside of the container, and it's accessible via the container's IP address on port 8080. We're going to dive into that in the coming lesson on networking. By default, Docker containers run inside of their own network, called the bridge network. However, it's really not clear how we interact with this web app. So if I list off the containers, you can see based on the status here that that container is up and running. And then we have access to our prompt again. Okay, there, notice the container ID is printed to the screen. So this allows us to run containers in the background. So for this flag, D stands for detach, as in Docker detaches from standard I/O and instead just prints the container ID, and then it's going to return us to our prompt. Docker allows us to run the process in the background with the minus D flag. Now really this is no different than if we ran this outside of Docker. So the web application is running indefinitely and waiting for connections.Īnd while it's running, we're unable to interact with our bash prompt. It's just running forever, serving up this website until we stop it.

#Docker container port mapping code#

This is expected, because the code is running inside of the container in an infinite loop. Let's run this container with the docker run command. And we can see it here in the list of images. Okay, let's build this image, and then we can start up the container based on the image. So it's going to actually execute that binary. And then it sets the default command to be the web app. It copies the web app binary into the container at the root directory, and then it exposes port 8080 from the container.Īnd we'll talk about this in a bit. If I print off the Docker file to the terminal, you can see that it uses the scratch base image. I have the web application compiled into a binary named web app, and it's in the same directory as the Docker file.

It's going to run on port 8080 and serve up just a bit of markup. The important part to know is that this is a basic web app. I'm not going to go through all of this code. The first is the root URL, and then there's this other endpoint at slash host which will display the host name and some environment variables. It's an application written in Go, and it has two URL endpoints. Here's the web application we're going to run. Now it's time to run something a bit more complex. So far the code that we've run inside of containers has been writing some text to standard output.