Embedded Wizard is intended to develop the GUI application and the navigation/business logic behind it. Of course you can integrate any kind of your own networking subsystems or other external library, as long as it provides a 'C' interface.
In the practice, we recommend to encapsulate all aspects of communication and data exchange within so-called driver classes. Such classes serve as interfaces between the GUI and the outer system. So within the GUI you communicate with the object of your driver class only. Within the driver class you can then implement code to call 'C' functions, etc. Even when the target system or the subsystem is changed later, you only need to adapt the driver class and the GUI application should run on the new system.
With the concept of 'Notifications' you can additionally use the driver class as a kind of broadcaster. GUI components can register themselves as observers for notifications coming from the driver and they can update themselves automatically. A simple example of a driver class can be found in the 'Quick Tour' example delivered with Embedded Wizard.