InvokeRegistry

ISOAPHeaders is the interface for accessing the headers of a SOAP envelope. It defines methods for adding headers that are sent with an outgoing message and for retrieving the headers that were included in an incoming message. 

On the server, the implementation class for in invokable interface supports this interface. You can obtain a reference to the ISOAPHeaders interface from the implementation class (a TInvokableClass descendant). You can then use this interface to retrieve the headers that were included in an incoming request or to add headers to an outgoing response message. If your implementation class does not descend from TInvokableClass, you can obtain a reference to this interface using the global GetSOAPHeaders function. 

For client-side header support, TRIO implements the ISOAPHeaders interface. However, you can't obtain an ISOAPHeaders interface directly from a remote interfaced object, because when you try to obtain an interface from TRIO or one of its descendants, it assumes that you are trying to obtain an invokable interface for a server object and generates an in-memory vtable. Instead, you must access the ISOAPHeaders interface from the invokable interface that the remote interface object supports.

TRIO 

TInvokableClass 

TSOAPHeaders 

GetSOAPHeaders 

Defining and Using SOAP Headers 

Processing Headers in Client Applications