function IdStackFactory: TIdStack;

TIdStack - The protocol stack instance to use for the platform hosting the application.

IdStackFactory is a TIdStack function used to initialize the global stack instance for the Indy library. IdStackFactory isolates the differences between protocol stack implementations on the platforms where Indy is supported. 

IdStackFactory uses the class reference in GStackClass to create the global stack instance in GStack. 

IdStackFactory also sets the HostName for the global stack instance by calling the ReadHostName function in the global stack instance. 

IdStackFactory is called when the Indy library is initialized.