BACnetStack_SendReadProperty

bool BACnetStack_SendReadProperty(
  uint8_t * sentInvokeId,
  const uint8_t serviceType,
  const uint8_t * connectionString,
  const uint8_t connectionStringLength,
  const uint32_t networkPortInstance,
  const uint16_t destinationNetwork,
  const uint8_t * destinationAddress,
  const uint8_t destinationAddressLength,
  const uint32_t propertyArraysCount,
  const void * propertyArrays,
  const uint32_t propertyArraysLength);

Sends a ReadProperty or ReadPropertyMultiple request.

BACnetStack_SendReadProperty()

One call serves both ReadProperty and ReadPropertyMultiple, selected by serviceType: serviceType = 12 (ReadProperty) -> propertyArraysCount must be 1 serviceType = 14 (ReadPropertyMultiple) -> propertyArraysCount >= 1

propertyArrays: propertyArraysCount packed elements, each CASBACnetStack::BACnetStackReadPropertyAsync::SIZE_OF_ARRAY bytes. Multi-byte fields are little-endian, the byte order of every host the stack supports:

*  +-[0]-----------*-[1][2]--------------*-[3][4][5][6]------------*-[7][8][9][10]---------------*-[11][12][13][14]------------*
*  | uint8_t flags | uint16_t objectType | uint32_t objectInstance | uint32_t propertyIdentifier | uint32_t propertyArrayIndex |
*  +---------------*---------------------*-------------------------*-----------------------------*-----------------------------*
*

uint8_t flags
  1 (0) = Use propertyArrayIndex
  2 (1) = (Reserved)
  4 (2) = (Reserved)
  8 (3) = (Reserved)
 16 (4) = (Reserved)
 32 (5) = (Reserved)
 64 (6) = (Reserved)
128 (7) = (Reserved)

Worked example - ReadProperty (serviceType 12), Analog Input 1’s Present_Value, no array index:

*     00   00 00   01 00 00 00   55 00 00 00   00 00 00 00        (15 bytes total)
*     |fl| |objType||objInstance||propertyId  ||arrayIndex  |
*

propertyArraysCount = 1, propertyArraysLength = 15. (objectType 0 = analog-input, propertyIdentifier 85 = Present_Value - see CASBACnetStack::BACnetObjectType and CASBACnetStack::BACnetPropertyIdentifier.)

BACnetStack_SendReadPropertyWithLength() below has an identical signature; both exports exist side by side.

See also: Client response hooks

BACnet reference: ANSI/ASHRAE 135-2024 clause 15.5 (ReadProperty Service); clause 15.7 (ReadPropertyMultiple Service).

Parameters

Parameter	Direction	Description
`sentInvokeId`	out	The invoke-id of the sent request, valid only if this function returns true.
`serviceType`	in	12 = ReadProperty, 14 = ReadPropertyMultiple; selects which service is sent.
`connectionString, connectionStringLength`	in	The datalink address to send TO (the destination) - not the local address to send from. For IPv4 this is 6 bytes: 4 octets of IPv4 address followed by 2 octets of port, big-endian (e.g. 0xC0,0xA8,0x01,0x05,0xBA,0xC0 = 192.168.1.5:47808; see BACnetStack_SendRegisterForeignDevice() for a worked example); on BACnet/IPv4 the stack refuses to send to a connection string of any other length, except that a broadcast from a device registered as a foreign device goes to its BBMD and does not use the connection string. MS/TP and BACnet/SC use a different connection-string shape; see their respective Set/Send exports.
`networkPortInstance`	in	The Network Port object instance to send the message on, or BACNET_NETWORK_PORT_DEFAULT (4194303) for the default/single port.
`destinationNetwork, destinationAddress, destinationAddressLength`	in	The destination to send the request to.
`propertyArraysCount, propertyArrays`	in	The packed property-reference array described above.
`propertyArraysLength`	in	The total byte length of propertyArrays (all elements concatenated). Enforced: rejects a propertyArraysCount that would read past this length.

Returns

True if the request was sent, otherwise false.

Topic: Client requests. Declared in CASBACnetStackDLL.h.