The Docker platform makes very few demands on applications that want to use it. You're not restricted to certain languages or frameworks, and you don't need to use special libraries to communicate from the app to the container and you don't need to structure your application in a certain way.
To support the widest possible range of applications, Docker uses the console to communicate between the application and the container runtime. Application logs and error messages are expected on the console output and error streams. Storage managed by Docker is presented as a normal disk to the operating system, and Docker's networking stack is transparent. The application appears to be running on its own machine, connected to other machines by a normal TCP/IP network.
A good citizen for Docker is an app that makes very few assumptions about the system it's running on and uses basic mechanisms that all operating systems support: the filesystem, environment variables...