% !TEX root = btstack_gettingstarted.tex
\section{GATT Client API}
\label{appendix:api_gatt_client}
$ $
\begin{lstlisting}
// Set up GATT client.
void gatt_client_init();

// Register callback (packet handler) for gatt client. Returns gatt client ID.
uint16_t gatt_client_register_packet_handler (gatt_client_callback_t callback);

// Unregister callback (packet handler) for gatt client.
void gatt_client_unregister_packet_handler(uint16_t gatt_client_id);

// Returns the GATT client context for the specified handle.
// gatt_client_t * get_gatt_client_context_for_handle(uint16_t con_handle);

// Returns if the gatt client is ready to receive a query. It is used with daemon.
int gatt_client_is_ready(uint16_t handle);

// Discovers all primary services. For each found service, an
// le_service_event_t with type set to GATT_SERVICE_QUERY_RESULT
// will be generated and passed to the registered callback.
// The gatt_complete_event_t, with type set to GATT_QUERY_COMPLETE,
// marks the end of discovery.
le_command_status_t gatt_client_discover_primary_services(uint16_t gatt_client_id, uint16_t con_handle);

// Discovers a specific primary service given its UUID. This service
// may exist multiple times. For each found service, an
// le_service_event_t with type set to GATT_SERVICE_QUERY_RESULT
// will be generated and passed to the registered callback.
// The gatt_complete_event_t, with type set to GATT_QUERY_COMPLETE,
// marks the end of discovery.
le_command_status_t gatt_client_discover_primary_services_by_uuid16(uint16_t gatt_client_id, uint16_t con_handle, uint16_t uuid16);
le_command_status_t gatt_client_discover_primary_services_by_uuid128(uint16_t gatt_client_id, uint16_t con_handle, const uint8_t * uuid);

// Finds included services within the specified service. For each
// found included service, an le_service_event_t with type set to
// GATT_INCLUDED_SERVICE_QUERY_RESULT will be generated and passed
// to the registered callback. The gatt_complete_event_t with type
// set to GATT_QUERY_COMPLETE, marks the end of discovery.
//
// Information about included service type (primary/secondary) can
// be retrieved either by sending an ATT find information request
// for the returned start group handle (returning the handle and
// the UUID for primary or secondary service) or by comparing the
// service to the list of all primary services.
le_command_status_t gatt_client_find_included_services_for_service(uint16_t gatt_client_id, uint16_t con_handle, le_service_t *service);

// Discovers all characteristics within the specified service. For
// each found characteristic, an le_characteristics_event_t with 
// type set to GATT_CHARACTERISTIC_QUERY_RESULT will be generated 
// and passed to the registered callback. The gatt_complete_event_t 
// with type set to GATT_QUERY_COMPLETE, marks the end of discovery.
le_command_status_t gatt_client_discover_characteristics_for_service(uint16_t gatt_client_id, uint16_t con_handle, le_service_t *service);

// The following four functions are used to discover all 
// characteristics within the specified service or handle range, and 
// return those that match the given UUID. For each found
// characteristic, an le_characteristic_event_t with type set to   
// GATT_CHARACTERISTIC_QUERY_RESULT will be generated and passed to 
// the registered callback. The gatt_complete_event_t with type set
// to GATT_QUERY_COMPLETE, marks the end of discovery.
le_command_status_t gatt_client_discover_characteristics_for_handle_range_by_uuid16(uint16_t gatt_client_id, uint16_t con_handle, uint16_t start_handle, uint16_t end_handle, uint16_t uuid16);
le_command_status_t gatt_client_discover_characteristics_for_handle_range_by_uuid128(uint16_t gatt_client_id, uint16_t con_handle, uint16_t start_handle, uint16_t end_handle, uint8_t * uuid);
le_command_status_t gatt_client_discover_characteristics_for_service_by_uuid16 (uint16_t gatt_client_id, uint16_t con_handle, le_service_t *service, uint16_t  uuid16);
le_command_status_t gatt_client_discover_characteristics_for_service_by_uuid128(uint16_t gatt_client_id, uint16_t con_handle, le_service_t *service, uint8_t * uuid128);

// Discovers attribute handle and UUID of a characteristic 
// descriptor within the specified characteristic. For each found
// descriptor, an le_characteristic_descriptor_event_t with 
// type set to GATT_CHARACTERISTIC_DESCRIPTOR_QUERY_RESULT will be  
// generated and passed to the registered callback. The  
// gatt_complete_event_t with type set to GATT_QUERY_COMPLETE, marks 
// the end of discovery.
le_command_status_t gatt_client_discover_characteristic_descriptors(uint16_t gatt_client_id, uint16_t con_handle, le_characteristic_t *characteristic);

// Reads the characteristic value using the characteristic's value
// handle. If the characteristic value is found, an 
// le_characteristic_value_event_t with type set to 
// GATT_CHARACTERISTIC_VALUE_QUERY_RESULT will be generated and
// passed to the registered callback. The gatt_complete_event_t 
// with type set to GATT_QUERY_COMPLETE, marks the end of read.
le_command_status_t gatt_client_read_value_of_characteristic(uint16_t gatt_client_id, uint16_t con_handle, le_characteristic_t *characteristic);
le_command_status_t gatt_client_read_value_of_characteristic_using_value_handle(uint16_t gatt_client_id, uint16_t con_handle, uint16_t characteristic_value_handle);

// Reads the long characteristic value using the characteristic's 
// value handle. The value will be returned in several blobs. For 
// each blob, an le_characteristic_value_event_t with type set to 
// GATT_CHARACTERISTIC_VALUE_QUERY_RESULT and updated value offset
// will be generated and passed to the registered callback. The 
// gatt_complete_event_t with type set to GATT_QUERY_COMPLETE, marks
// the end of read.
le_command_status_t gatt_client_read_long_value_of_characteristic(uint16_t gatt_client_id, uint16_t con_handle, le_characteristic_t *characteristic);
le_command_status_t gatt_client_read_long_value_of_characteristic_using_value_handle(uint16_t gatt_client_id, uint16_t con_handle, uint16_t characteristic_value_handle);
    
// Writes the characteristic value using the characteristic's value
// handle without an acknowledgement that the write was successfully
// performed.
le_command_status_t gatt_client_write_value_of_characteristic_without_response(uint16_t gatt_client_id, uint16_t con_handle, uint16_t characteristic_value_handle, uint16_t length, uint8_t * data);

// Writes the authenticated characteristic value using the
// characteristic's value handle without an acknowledgement
// that the write was successfully performed.
le_command_status_t gatt_client_signed_write_without_response(uint16_t gatt_client_id, uint16_t con_handle, uint16_t handle, uint16_t message_len, uint8_t * message, sm_key_t csrk, uint32_t sgn_counter);

// Writes the characteristic value using the characteristic's value
// handle. The gatt_complete_event_t with type set to
// GATT_QUERY_COMPLETE, marks the end of write. The write is
// successfully performed, if the event's status field is set to 0.
le_command_status_t gatt_client_write_value_of_characteristic(uint16_t gatt_client_id, uint16_t con_handle, uint16_t characteristic_value_handle, uint16_t length, uint8_t * data);
le_command_status_t gatt_client_write_long_value_of_characteristic(uint16_t gatt_client_id, uint16_t con_handle, uint16_t characteristic_value_handle, uint16_t length, uint8_t * data);

// Writes of the long characteristic value using the
// characteristic's value handle. It uses server response to
// validate that the write was correctly received.
// The gatt_complete_event_t with type set to GATT_QUERY_COMPLETE
// marks the end of write. The write is successfully performed, if
// the event's status field is set to 0.
le_command_status_t gatt_client_reliable_write_long_value_of_characteristic(uint16_t gatt_client_id, uint16_t con_handle, uint16_t characteristic_value_handle, uint16_t length, uint8_t * data);

// Reads the characteristic descriptor using its handle. If the
// characteristic descriptor is found, an
// le_characteristic_descriptor_event_t with type set to
// GATT_CHARACTERISTIC_DESCRIPTOR_QUERY_RESULT will be generated
// and passed to the registered callback. The gatt_complete_event_t
// with type set to GATT_QUERY_COMPLETE, marks the end of read.
le_command_status_t gatt_client_read_characteristic_descriptor(uint16_t gatt_client_id, uint16_t con_handle, le_characteristic_descriptor_t * descriptor);

// Reads the long characteristic descriptor using its handle. It
// will be returned in several blobs.  For each blob, an
// le_characteristic_descriptor_event_t with type set to
// GATT_CHARACTERISTIC_DESCRIPTOR_QUERY_RESULT will be generated
// and passed to the registered callback. The gatt_complete_event_t
// with type set to GATT_QUERY_COMPLETE, marks the end of read.
le_command_status_t gatt_client_read_long_characteristic_descriptor(uint16_t gatt_client_id, uint16_t con_handle, le_characteristic_descriptor_t * descriptor);

// Writes the characteristic descriptor using its handle.
// The gatt_complete_event_t with type set to
// GATT_QUERY_COMPLETE, marks the end of write. The write is
// successfully performed, if the event's status field is set to 0.
le_command_status_t gatt_client_write_characteristic_descriptor(uint16_t gatt_client_id, uint16_t con_handle, le_characteristic_descriptor_t * descriptor, uint16_t length, uint8_t * data);
le_command_status_t gatt_client_write_long_characteristic_descriptor(uint16_t gatt_client_id, uint16_t con_handle, le_characteristic_descriptor_t * descriptor, uint16_t length, uint8_t * data);

// Writes the client characteristic configuration of the specified 
// characteristic. It is used to subscribe for notifications or 
// indications of the characteristic value. For notifications or 
// indications specify:
// GATT_CLIENT_CHARACTERISTICS_CONFIGURATION_NOTIFICATION resp. 
// GATT_CLIENT_CHARACTERISTICS_CONFIGURATION_INDICATION 
// as configuration value.
le_command_status_t gatt_client_write_client_characteristic_configuration(uint16_t gatt_client_id, uint16_t con_handle, le_characteristic_t * characteristic, uint16_t configuration);
\end{lstlisting}
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