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ORG.BLUEZ.GATTCHARACTERISTIC(5) Linux System Administration ORG.BLUEZ.GATTCHARACTERISTIC(5)

NAME

org.bluez.GattCharacteristic - BlueZ D-Bus GattCharacteristic API documentation

DESCRIPTION

GATT local/server and remote/client characteristic attribute representation share the same high-level D-Bus API.

Local/Server refers to GATT based characteristics exported by a plugin or an external application.

Remote/Client refers to GATT characteristics exported by the peer.

INTERFACE

Client

org.bluez
org.bluez.GattCharacteristic1
[variable prefix]/{hci0,hci1,...}/dev_XX_XX_XX_XX_XX_XX/serviceXX/charYYYY

Server

unique name
org.bluez.GattCharacteristic1
freely definable

Methods

array{byte} ReadValue(dict options)

Issues a request to read the value of the characteristic and returns the value if the operation was successful.

Possible options:

Read start offset in bytes.
Exchange MTU in bytes.
Device object.
Link type.

Possible values:

"BR/EDR"
"LE"


Possible Errors:

Possible values: string 0x80 - 0x9f



void WriteValue(array{byte} value, dict options)

Issues a request to write the value of the characteristic.

Possible options:

Write start offset in bytes.
Possible values:
"command"
Use Write without response procedure.
"request"
Use Write with response procedure.
"reliable"
Use Reliable Write procedure.

Exchanged MTU (Server only).
Device path (Server only).
Link type (Server only).

Possible values:

"BR/EDR"
"LE"

True if prepare authorization request.

Possible Errors:

Possible values: string 0x80 - 0x9f



fd, uint16 AcquireWrite(dict options) [optional]

Acquire file descriptor and MTU for writing. Only sockets are supported. Usage of WriteValue will be locked causing it to return NotPermitted error.

For server the MTU returned shall be equal or smaller than the negotiated MTU.

For client it only works with characteristic that has WriteAcquired property which relies on write-without-response Flag.

To release the lock the client shall close the file descriptor, a HUP is generated in case the device is disconnected.

Note: the MTU can only be negotiated once and is symmetric therefore this method may be delayed in order to have the exchange MTU completed, because of that the file descriptor is closed during reconnections as the MTU has to be renegotiated.

Possible options:

Object Device (Server only).
Exchanged MTU (Server only).
Link type (Server only).

Possible values:

"BR/EDR"
"LE"


Possible Errors:




fd, uint16 AcquireNotify(dict options) [optional]

Acquire file descriptor and MTU for notify. Only sockets are support.

Usage of StartNotify will be locked causing it to return org.bluez.Error.NotPermitted.

For server the MTU returned shall be equal or smaller than the negotiated MTU.

Only works with characteristic that has NotifyAcquired property which relies on "notify" Flag and no other client have called StartNotify().

Notification are enabled during this procedure so StartNotify() shall not be called, any notification will be dispatched via file descriptor therefore the Value property is not affected during the time where notify has been acquired.

To release the lock the client shall close the file descriptor, a HUP is generated in case the device is disconnected.

Note: the MTU can only be negotiated once and is symmetric therefore this method may be delayed in order to have the exchange MTU completed, because of that the file descriptor is closed during reconnections as the MTU has to be renegotiated.

Possible options:

Object Device (Server only).
Exchanged MTU (Server only).
Link type (Server only).

Possible values:

"BR/EDR"
"LE"


Possible Errors:




void StartNotify()

Starts a notification session from this characteristic if it supports value notifications or indications.

Possible Errors:




void StopNotify()

Stops or cancel session previously created by StartNotify().

Note that notifications from a characteristic are shared between sessions thus calling StopNotify will release a single session.

Possible Errors:




void Confirm() [noreply, optional] (Server only)

Confirms value was received.

Possible Errors:

org.bluez.Error.Failed



Properties

string UUID [read-only]

128-bit characteristic UUID.


object Service [read-only]

Object path of the GATT service the characteristic belongs to.


array{byte} Value [read-only, optional]

The cached value of the characteristic. This property gets updated only after a successful read request and when a notification or indication is received, upon which a PropertiesChanged signal will be emitted.


boolean WriteAcquired [read-only, optional]

True, if this characteristic has been acquired by any client using AcquireWrite.

For client properties is ommited in case 'write-without-response' flag is not set.

For server the presence of this property indicates that AcquireWrite is supported.



boolean NotifyAcquired [read-only, optional]

True, if this characteristic has been acquired by any client using AcquireNotify.

For client this properties is ommited in case 'notify' flag is not set.

For server the presence of this property indicates that AcquireNotify is supported.



boolean Notifying [read-only, optional]

True, if notifications or indications on this characteristic are currently enabled.


array{string} Flags [read-only]

Defines how the characteristic value can be used. See Core spec "Table 3.5: Characteristic Properties bit field", and "Table 3.8: Characteristic Extended Properties bit field".

The "x-notify" and "x-indicate" flags restrict access to notifications and indications by imposing write restrictions on a characteristic's client characteristic configuration descriptor.

Possible values:

"broadcast"
"read"
"write-without-response"
"write"
"notify"
"indicate"
"authenticated-signed-writes"
"extended-properties"
"reliable-write"
"writable-auxiliaries"
"encrypt-read"
"encrypt-write"
"encrypt-notify" (Server only)
"encrypt-indicate" (Server only)
"encrypt-authenticated-read"
"encrypt-authenticated-write"
"encrypt-authenticated-notify" (Server only)
"encrypt-authenticated-indicate" (Server only)
"secure-read" (Server only)
"secure-write" (Server only)
"secure-notify" (Server only)
"secure-indicate" (Server only)
"authorize"



uint16 Handle [read-only] (Client Only)

Characteristic handle.


uint16 Handle [read-write, optional] (Server Only)

Characteristic handle. When available in the server it would attempt to use to allocate into the database which may fail, to auto allocate the value 0x0000 shall be used which will cause the allocated handle to be set once registered.


uint16 MTU [read-only]

Characteristic MTU, this is valid both for ReadValue() and WriteValue() but either method can use long procedures when supported.


October 2023 BlueZ