For communication between applications, Internal Load Balancer can be used (click here to read more about load balancers). Application that want to send request to other application, should send request to the local Internal Load Balancer available at port 8021. Applications in Docker containers can use
onteon-host DNS name.
In the image you can see how App #1 access App #5, via the Internal Load Balancer.
To access a proper application, you need to create a proper url. You can access application by name and by name and version.