Each interface is a combination of two modules, external (aka adapter) and internal (aka receiver). For example, interface for HTTP protocol consists of two modules - http_interface.py and http_interface_receiver.py. The external half handles the protocol-specific details which are not supposed to change. The receiver is the entry point to the aplication-specific processing and is just a regular reloadable application module, which just happens to be the first to see the request received from the client.

The receiver module is thus the first reloadable application module on the request's way, and in most cases it is the receiver module which you will have to modify to implement your own request processing. More on application-specific request processing in the application modules section.

As per the above diagram, more than one interface of the same kind can be enabled on a cage by having multiple copies of the adapter module. Nevertheless, all the requests still arrive to the same single receiver module.