This article will explain the following content:
What is the “EXPOSE Port”?
The “Expose Port” feature is a way to declare that a container listens on a certain network port during execution. It is used to expose a container’s network port to the host system or other containers. It permits users to specify a port number on the container that will be mapped to a port number on the host. This way, users can access the service executing on the container utilizing the IP address of host and port number. Users can specify these ports as either UDP or TCP. However, TCP is the default protocol.
The syntax to EXPOSE the ports is:
Users can specify one or more ports to be exposed by using multiple EXPOSE statements in your Docker file.
Significance of the “EXPOSE Port”
The significance of this “EXPOSE Port” instruction is that it permits containers to communicate with each other. It also allows containers to communicate with the host machine, which is useful for running web applications and other network services.
Moreover, it enables developers to document the network ports that their container image uses. This can be helpful for other developers who want to use or build upon that container image, as they can easily see which ports the image is listening to and how they can use them.
Limitations of the “EXPOSE Port”
The main limitation of the “EXPOSE Port” instruction is that it does not actually publish the port or make it accessible from outside the container. It simply informs Docker that the container is listening on that port at runtime.
Another limitation is that if a container is listening on a port that is already in use by the host machine, exposing that port will result in a conflict. Moreover, it does not provide any security or access control for the exposed port.
Conclusion
The “EXPOSE Port” instruction is significant in documenting the network ports that a container image uses. It enables communication between containers and the host system or other containers. It permits other containers or external systems to access the container’s services running on the exposed port. However, it also has limitations related to security and port conflicts. This article has explained the significance and limitations of the “EXPOSE Port” feature in Docker.
