The GetDevCaps packet is transmitted from a TAPI client to a TAPI server in a remote procedure call. Sending this packet queries a specified line device to determine its telephony capabilities. The returned information is valid for all addresses on the line device.

Req_Func (4 bytes): An unsigned 32-bit integer. The identifier of the function that is invoked on the remote server. This value MUST be set to 34.

Return Values

On completion of ClientRequest, this field contains the result of the encapsulated telephony request. A value of 0 indicates success, and a LINEERR_Constants value indicates failure. The remote server MUST complete this call synchronously.

MUST return zero if the function succeeds or an error number if an error occurs. Common return values are as follows:

Name	Value
LINEERR_INCOMPATIBLEAPIVERSION	0x8000000C
LINEERR_INCOMPATIBLEEXTVERSION	0x8000000D
LINEERR_NODRIVER	0x80000043
LINEERR_NOMEM	0x80000044
LINEERR_OPERATIONFAILED	0x80000048
LINEERR_OPERATIONUNAVAIL	0x80000049
LINEERR_RESOURCEUNAVAIL	0x8000004B

Reserved1 (4 bytes): An unsigned 32-bit integer. MUST be set to zero when sent and MUST be ignored on receipt.

hLineApp (4 bytes): An HLINEAPP. A handle to the client application's registration with TAPI. This field MUST have been obtained by sending the Initialize packet.

dwDeviceID (4 bytes): An unsigned 32-bit integer. The line device to be queried. A valid value of dwDeviceID is in the range 0 to dwNumDevs – 1. The client obtains dwNumDevs by sending a Initialize packet to the remote server.

dwTSPIVersion (4 bytes): An unsigned 32-bit integer. The negotiated TSPI version number. This value has already been negotiated for this device through the NegotiateAPIVersion packet.

dwExtVersion (4 bytes): An unsigned 32-bit integer. The negotiated extension version number. This value has already been negotiated for this device through the NegotiateExtVersion packet. This parameter is not validated by TAPI when this function is called.

lpLineDevCaps (4 bytes): An unsigned 32-bit integer. The size, in bytes, of a LINEDEVCAPS data packet that is filled with line device capabilities information upon successful completion of the request.

On successful completion, this field contains the offset, in bytes, of the data packet in the VarData field.

Reserved2 (4 bytes): An unsigned 32-bit integer. This field is used for padding and MUST be ignored on receipt. It can be any value.

Reserved3 (4 bytes): An unsigned 32-bit integer. This field is used for padding and MUST be ignored on receipt. It can be any value.

Reserved4 (4 bytes): An unsigned 32-bit integer. This field is used for padding and MUST be ignored on receipt. It can be any value.

Reserved5 (4 bytes): An unsigned 32-bit integer. This field is used for padding and MUST be ignored on receipt. It can be any value.

Reserved6 (4 bytes): An unsigned 32-bit integer. This field is used for padding and MUST be ignored on receipt. It can be any value.

Reserved7 (4 bytes): An unsigned 32-bit integer. This field is used for padding and MUST be ignored on receipt. It can be any value.

Reserved8 (4 bytes): An unsigned 32-bit integer. This field is used for padding and MUST be ignored on receipt. It can be any value.

Reserved9 (4 bytes): An unsigned 32-bit integer. This field is used for padding and MUST be ignored on receipt. It can be any value.

VarData (variable): MUST be present on successful completion of the request. MUST contain a LINEDEVCAPS data structure.

The contents of this field MUST be DWORD-aligned, as specified in [MS-DTYP] section 2.2.9.