2.2.1 Common Order Header (ORDER_HDR)

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The messages, or protocol data unit (PDU), exchanged as part of this protocol MUST start with the Common Order Header (ORDER_HDR), which identifies the type of message contained in the PDU payload and the length of the payload, in bytes. As multiple messages for this protocol can be encapsulated in a single lower-level transport PDU, the Common Order Header allows receivers to calculate the message boundaries.


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Type

Length

Type (2 bytes): A 16-bit, unsigned integer that specifies the type of the PDU that follows the Length field.

Value

Meaning

ODTYPE_FILTER_STATE_UPDATED

0x0001

Indicates a Filter-Updated PDU (OD_FILTER_STATE_UPDATED) (section 2.2.3.1).

ODTYPE_APP_REMOVED

0x0002

Indicates an Application-Removed PDU (OD_APP_REMOVED) (section 2.2.3.3).

ODTYPE_APP_CREATED

0x0003

Indicates an Application-Created PDU (OD_APP_CREATED) (section 2.2.3.2).

ODTYPE_WND_REMOVED

0x0004

Indicates a Window-Removed PDU (OD_WND_REMOVED) (section 2.2.3.5).

ODTYPE_WND_CREATED

0x0005

Indicates a Window-Created PDU (OD_WND_CREATED) (section 2.2.3.4).

ODTYPE_WND_SHOW

0x0006

Indicates a Show Window PDU (OD_WND_SHOW) (section 2.2.3.6).

ODTYPE_PARTICIPANT_REMOVED

0x0007

Indicates a Participant-Removed PDU (OD_PARTICIPANT_REMOVED) (section 2.2.4.2).

ODTYPE_PARTICIPANT_CREATED

0x0008

Indicates a Participant-Created PDU (OD_PARTICIPANT_CREATED) (section 2.2.4.1).

ODTYPE_PARTICIPANT_CTRL_CHANGED

0x0009

Indicates a Change Participant Control Level PDU (OD_PARTICIPANT_CTRL_CHANGE) (section 2.2.4.3).

ODTYPE_GRAPHICS_STREAM_PAUSED

0x000A

Indicates a Graphics Stream-Paused PDU (OD_GRAPHICS_STREAM_PAUSED) (section 2.2.5.1).

ODTYPE_GRAPHICS_STREAM_RESUMED

0x000B

Indicates a Graphics Stream-Resumed PDU (OD_GRAPHICS_STREAM_RESUMED) (section 2.2.5.2).

ODTYPE_WND_RGN_UPDATE

0x000C

Indicates a Window Region Update PDU (OD_WINDOW_REGION_UPDATE) (section 2.2.3.7).

ODTYPE_PARTICIPANT_CTRL_CHANGE_RESPONSE

0x000D

Indicates a Change Participant Control Level Response PDU (OD_PARTICIPANT_CTRL_CHANGE_RESPONSE) (section 2.2.4.4).

Length (2 bytes): A 16-bit, unsigned integer that specifies the length of the data, in bytes, contained by the PDU. This field MUST be the payload size plus the size of the common header and MUST be used in decoding the individual PDUs.