1.3.2.1 Interface Manipulation

In the context of the Remote Desktop Protocol: XPS Print Virtual Channel Extension, interfaces are groups of messages with a common identifier. The Remote Desktop Protocol: XPS Print Virtual Channel Extension includes a common infrastructure for manipulating these interfaces, called Interface Manipulation. This infrastructure consists of Interface Query and Interface Release messages. A newer version of an interface can be retrieved by sending an Interface Query message. In addition, to keep the number of active interfaces on the network low, an interface is terminated by means of an Interface Release message.

Interfaces are identified by interface identifiers (InterfaceIds, section 3.1.1). An InterfaceId, together with a function ID (FunctionId, section 3.1.1), uniquely identifies the request message. FunctionIds are explicitly specified only in request messages. Reply packets contain only message IDs (MessageId, section 3.1.1), and hence implicitly contain the FunctionId for which they were associated. A further differentiation exists between InterfaceIds and MessageIds originating from either the client or the server side of the connection. The uniqueness of these IDs is guaranteed only for those InterfaceIds that originate from the same side of the connection. This means that a request from server to client with InterfaceId 1 and MessageId 2 is different than a request with the same IDs from the client side. The same is true for replies.