2.2.1 Shared Message Header (SHARED_MSG_HEADER)

Every packet in this extension contains a common header.<1>

InterfaceId (4 bytes): The InterfaceId field is broken out as follows:

InterfaceValue (30 bits): A 30-bit unsigned integer that represents the common identifier for the interface. The default value is 0x00000000. If the message uses this default interface ID, the message is interpreted for the main interface for which this channel has been instantiated. All other values MUST be retrieved either from an Interface Query response (QI_RSP), [MS-RDPEXPS] section2.2.2.1.2, or from responses that contain interface IDs.

This ID is valid until an interface release (IFACE_RELEASE) message ([MS-RDPEXPS] section 2.2.2.2) is sent or received with that ID. After an IFACE_RELEASE message is processed, this ID is considered invalid.

Mask (2 bits): These two bits in the SHARED_MSG_HEADER header MUST be set to one of the following values.

Value	Meaning
STREAM_ID_STUB 0x80000000	Indicates that the SHARED_MSG_HEADER is being used in a response message.
STREAM_ID_PROXY 0x40000000	Indicates that the SHARED_MSG_HEADER is not being used in a response message.
STREAM_ID_NONE 0x00000000	Indicates that the SHARED_MSG_HEADER is being used for interface manipulation capabilities exchange as specified in section 2.2.3. This value MUST NOT be used for any other messages.

MessageId (4 bytes): A 32-bit unsigned integer that represents a unique ID for the request or response pair. Requests and responses are matched based on this ID coupled with the InterfaceId.

FunctionId (4 bytes): A 32-bit unsigned integer. This field MUST be present in all packets except response packets. Its value is either used in interface manipulation messages or defined for a specific interface. The following values are categorized by the interface for which they are defined.

Common IDs for all interfaces are as follows.

Value	Meaning
RIMCALL_RELEASE 0x00000001	Release the given interface ID.
RIMCALL_QUERYINTERFACE 0x00000002	Query for a new interface.

The Capabilities Negotiator Interface ID is as follows.

Value	Meaning
RIM_EXCHANGE_CAPABILITY_REQUEST 0x00000100	The server sends the Interface Manipulation Exchange Capabilities Request message.

The Client Notifications Interface IDs are as follows.

Value	Meaning
PLAYBACK_ACK 0x00000100	The client sends the Playback Acknowledgment message.
CLIENT_EVENT_NOTIFICATION 0x00000101	The client sends the Client Event Notification message.

Server Data Interface IDs are as follows.

Value	Meaning
EXCHANGE_CAPABILITIES_REQ 0x00000100	The server sends the Exchange Capabilities Request message.
SET_CHANNEL_PARAMS 0x00000101	The server sends the Set Channel Parameters message.
ADD_STREAM 0x00000102	The server sends the Add Stream message.
ON_SAMPLE 0x00000103	The server sends the On Sample message.
SET_VIDEO_WINDOW 0x00000104	The server sends the Set Video Window message.
ON_NEW_PRESENTATION 0x00000105	The server sends the New Presentation message.
SHUTDOWN_PRESENTATION REQ 0x00000106	The server sends the Shut Down Presentation Request message.
SET_TOPOLOGY_REQ 0x00000107	The server sends the Set Topology Request message.
CHECK_FORMAT_SUPPORT_REQ 0x00000108	The server sends the Check Format Support Request message.
ON_PLAYBACK_STARTED 0x00000109	The server sends the On Playback Started message.
ON_PLAYBACK_PAUSED 0x0000010a	The server sends the On Playback Paused message.
ON_PLAYBACK_STOPPED 0x0000010b	The server sends the On Playback Stopped message.
ON_PLAYBACK_RESTARTED 0x0000010c	The server sends the On Playback Restarted message.
ON_PLAYBACK_RATE_CHANGED 0x0000010d	The server sends the On Playback Rate Change message.
ON_FLUSH 0x0000010e	The server sends the On Flush message.
ON_STREAM_VOLUME 0x0000010f	The server sends the On Stream Volume message.
ON_CHANNEL_VOLUME 0x00000110	The server sends the On Channel Volume message.
ON_END_OF_STREAM 0x00000111	The server sends the On End of Stream message.
SET_ALLOCATOR 0x00000112	The server sends the Set Allocator Properties message.
NOTIFY_PREROLL 0x00000113	The server sends the Notify Preroll message.
UPDATE_GEOMETRY_INFO 0x00000114	The server sends the Update Geometry Information message.
REMOVE_STREAM 0x00000115	The server sends the Remove Stream message.
SET_SOURCE_VIDEO_RECT 0x00000116	The server sends the Set Source Video Rectangle message.

messagePayload (variable): An array of unsigned 8-bit integers describing the payload of the message corresponding to the interface for which the packet is sent. The specific structure of the payload is described by the message descriptions in sections 2.2.3, 2.2.4, and 2.2.5.