BlueZ D-Bus GATT API description ******************************** GATT local and remote services share the same high-level D-Bus API. Local refers to GATT based service exported by a BlueZ plugin or an external application. Remote refers to GATT services exported by the peer. BlueZ acts as a proxy, translating ATT operations to D-Bus method calls and Properties (or the opposite). Support for D-Bus Object Manager is mandatory for external services to allow seamless GATT declarations (Service, Characteristic and Descriptors) discovery. Each GATT service tree is required to export a D-Bus Object Manager at its root that is solely responsible for the objects that belong to that service. Releasing a registered GATT service is not defined yet. Any API extension should avoid breaking the defined API, and if possible keep an unified GATT remote and local services representation. Service hierarchy ================= GATT remote and local service representation. Object path for local services is freely definable. External applications implementing local services must register the services using GattManager1 registration method and must implement the methods and properties defined in GattService1 interface. Service org.bluez Interface org.bluez.GattService1 Object path [variable prefix]/{hci0,hci1,...}/dev_XX_XX_XX_XX_XX_XX/serviceXX Properties string UUID [read-only] 128-bit service UUID. boolean Primary [read-only] Indicates whether or not this GATT service is a primary service. If false, the service is secondary. object Device [read-only, optional] Object path of the Bluetooth device the service belongs to. Only present on services from remote devices. array{object} Includes [read-only, optional] Array of object paths representing the included services of this service. uint16 Handle [read-write, optional] (Server Only) Service 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. Characteristic hierarchy ======================== For local GATT defined services, the object paths need to follow the service path hierarchy and are freely definable. Service org.bluez Interface org.bluez.GattCharacteristic1 Object path [variable prefix]/{hci0,hci1,...}/dev_XX_XX_XX_XX_XX_XX/serviceXX/charYYYY 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: "offset": uint16 offset "mtu": Exchanged MTU (Server only) "device": Object Device (Server only) Possible Errors: org.bluez.Error.Failed(string ecode) org.bluez.Error.InProgress org.bluez.Error.NotPermitted org.bluez.Error.NotAuthorized org.bluez.Error.InvalidOffset org.bluez.Error.NotSupported Possible Error Code: string 0x80 - 0x9f void WriteValue(array{byte} value, dict options) Issues a request to write the value of the characteristic. Possible options: "offset": Start offset "type": string Possible values: "command": Write without response "request": Write with response "reliable": Reliable Write "mtu": Exchanged MTU (Server only) "device": Device path (Server only) "link": Link type (Server only) "prepare-authorize": True if prepare authorization request Possible Errors: org.bluez.Error.Failed(string ecode) org.bluez.Error.InProgress org.bluez.Error.NotPermitted org.bluez.Error.InvalidValueLength org.bluez.Error.NotAuthorized org.bluez.Error.NotSupported Possible Error Code: 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: "device": Object Device (Server only) "mtu": Exchanged MTU (Server only) "link": Link type (Server only) Possible Errors: org.bluez.Error.Failed org.bluez.Error.NotSupported 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 NotPermitted error. For server the MTU returned shall be equal or smaller than the negotiated MTU. Only works with characteristic that has NotifyAcquired 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: "device": Object Device (Server only) "mtu": Exchanged MTU (Server only) "link": Link type (Server only) Possible Errors: org.bluez.Error.Failed org.bluez.Error.NotSupported void StartNotify() Starts a notification session from this characteristic if it supports value notifications or indications. Possible Errors: org.bluez.Error.Failed org.bluez.Error.NotPermitted org.bluez.Error.InProgress org.bluez.Error.NotConnected org.bluez.Error.NotSupported void StopNotify() This method will cancel any previous StartNotify transaction. Note that notifications from a characteristic are shared between sessions thus calling StopNotify will release a single session. Possible Errors: org.bluez.Error.Failed void Confirm() [optional] (Server only) This method doesn't expect a reply so it is just a confirmation that 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. Allowed 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-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. Characteristic Descriptors hierarchy ==================================== Local or remote GATT characteristic descriptors hierarchy. Service org.bluez Interface org.bluez.GattDescriptor1 Object path [variable prefix]/{hci0,hci1,...}/dev_XX_XX_XX_XX_XX_XX/serviceXX/charYYYY/descriptorZZZ Methods array{byte} ReadValue(dict flags) Issues a request to read the value of the characteristic and returns the value if the operation was successful. Possible options: "offset": Start offset "device": Device path (Server only) "link": Link type (Server only) Possible Errors: org.bluez.Error.Failed org.bluez.Error.InProgress org.bluez.Error.NotPermitted org.bluez.Error.NotAuthorized org.bluez.Error.NotSupported void WriteValue(array{byte} value, dict flags) Issues a request to write the value of the characteristic. Possible options: "offset": Start offset "device": Device path (Server only) "link": Link type (Server only) "prepare-authorize": boolean Is prepare authorization request Possible Errors: org.bluez.Error.Failed org.bluez.Error.InProgress org.bluez.Error.NotPermitted org.bluez.Error.InvalidValueLength org.bluez.Error.NotAuthorized org.bluez.Error.NotSupported Properties string UUID [read-only] 128-bit descriptor UUID. object Characteristic [read-only] Object path of the GATT characteristic the descriptor belongs to. array{byte} Value [read-only, optional] The cached value of the descriptor. This property gets updated only after a successful read request, upon which a PropertiesChanged signal will be emitted. array{string} Flags [read-only] Defines how the descriptor value can be used. Possible values: "read" "write" "encrypt-read" "encrypt-write" "encrypt-authenticated-read" "encrypt-authenticated-write" "secure-read" (Server Only) "secure-write" (Server Only) "authorize" 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. GATT Profile hierarchy ===================== Local profile (GATT client) instance. By registering this type of object an application effectively indicates support for a specific GATT profile and requests automatic connections to be established to devices supporting it. Service Interface org.bluez.GattProfile1 Object path Methods void Release() This method gets called when the service daemon unregisters the profile. The profile can use it to do cleanup tasks. There is no need to unregister the profile, because when this method gets called it has already been unregistered. Properties array{string} UUIDs [read-only] 128-bit GATT service UUIDs to auto connect. GATT Manager hierarchy ====================== GATT Manager allows external applications to register GATT services and profiles. Registering a profile allows applications to subscribe to *remote* services. These must implement the GattProfile1 interface defined above. Registering a service allows applications to publish a *local* GATT service, which then becomes available to remote devices. A GATT service is represented by a D-Bus object hierarchy where the root node corresponds to a service and the child nodes represent characteristics and descriptors that belong to that service. Each node must implement one of GattService1, GattCharacteristic1, or GattDescriptor1 interfaces described above, based on the attribute it represents. Each node must also implement the standard D-Bus Properties interface to expose their properties. These objects collectively represent a GATT service definition. To make service registration simple, BlueZ requires that all objects that belong to a GATT service be grouped under a D-Bus Object Manager that solely manages the objects of that service. Hence, the standard DBus.ObjectManager interface must be available on the root service path. An example application hierarchy containing two separate GATT services may look like this: -> /com/example | - org.freedesktop.DBus.ObjectManager | -> /com/example/service0 | | - org.freedesktop.DBus.Properties | | - org.bluez.GattService1 | | | -> /com/example/service0/char0 | | - org.freedesktop.DBus.Properties | | - org.bluez.GattCharacteristic1 | | | -> /com/example/service0/char1 | | - org.freedesktop.DBus.Properties | | - org.bluez.GattCharacteristic1 | | | -> /com/example/service0/char1/desc0 | - org.freedesktop.DBus.Properties | - org.bluez.GattDescriptor1 | -> /com/example/service1 | - org.freedesktop.DBus.Properties | - org.bluez.GattService1 | -> /com/example/service1/char0 - org.freedesktop.DBus.Properties - org.bluez.GattCharacteristic1 When a service is registered, BlueZ will automatically obtain information about all objects using the service's Object Manager. Once a service has been registered, the objects of a service should not be removed. If BlueZ receives an InterfacesRemoved signal from a service's Object Manager, it will immediately unregister the service. Similarly, if the application disconnects from the bus, all of its registered services will be automatically unregistered. InterfacesAdded signals will be ignored. Examples: - Client test/example-gatt-client client/bluetoothctl - Server test/example-gatt-server tools/gatt-service Service org.bluez Interface org.bluez.GattManager1 Object path [variable prefix]/{hci0,hci1,...} Methods void RegisterApplication(object application, dict options) Registers a local GATT services hierarchy as described above (GATT Server) and/or GATT profiles (GATT Client). The application object path together with the D-Bus system bus connection ID define the identification of the application registering a GATT based service or profile. Possible errors: org.bluez.Error.InvalidArguments org.bluez.Error.AlreadyExists void UnregisterApplication(object application) This unregisters the services that has been previously registered. The object path parameter must match the same value that has been used on registration. Possible errors: org.bluez.Error.InvalidArguments org.bluez.Error.DoesNotExist