SDP(3)

SDP(3) | Library Functions Manual | SDP(3)

# NAME

`sdp_open`, `sdp_open_local`, `sdp_close`, `sdp_service_search`, `sdp_service_attribute`, `sdp_service_search_attribute`, `sdp_record_insert`, `sdp_record_update`, `sdp_record_remove` — Service Discovery Protocol session routines

# LIBRARY

Bluetooth Library (libbluetooth, -lbluetooth)

# SYNOPSIS

`#include <sdp.h>`

sdp_session_t
`sdp_open`(const bdaddr_t *laddr, const bdaddr_t *raddr);

sdp_session_t
`sdp_open_local`(const char *control);

void
`sdp_close`(sdp_session_t ss);

bool
`sdp_service_search`(sdp_session_t ss, const sdp_data_t *ssp, uint32_t *handlep, int *num);

bool
`sdp_service_attribute`(sdp_session_t ss, uint32_t handle, const sdp_data_t *ail, sdp_data_t *response);

bool
`sdp_service_search_attribute`(sdp_session_t ss, const sdp_data_t *ssp, const sdp_data_t *ail, sdp_data_t *response);

bool
`sdp_record_insert`(sdp_session_t ss, bdaddr_t *bdaddr, uint32_t *handlep, const sdp_data_t *record);

bool
`sdp_record_update`(sdp_session_t ss, uint32_t handle, sdp_data_t *record);

bool
`sdp_record_remove`(sdp_session_t ss, uint32_t handle);

# DESCRIPTION

The SDP library provides means for client programs to perform Bluetooth Service Discovery, and to advertise Service Records on the local host.

The Service Discovery API reflects the Bluetooth SDP specification, providing access to complete ServiceSearch, ServiceAttribute or ServiceSearchAttribute transactions and using SDP data element lists directly which can be constructed and parsed with the sdp_data(3) library functions.

The ServiceSearchPattern is a list of UUID data elements. The list must contain at least one UUID and the maximum number of UUIDs is 12. A service record will be matched when all the UUIDs from the ServiceSearchPattern are contained in the record.

The AttributeIDList is a list of data elements where each is either an attribute ID encoded as an unsigned 16-bit integer, or a range of attribute IDs encoded as an unsigned 32-bit integer where the high order 16-bits are the start of the range and the low order 16-bits are the end of the range (inclusive). The AttributeIDList should be arranged in ascending order and there should be no duplicate attribute ID values. If `NULL` is passed, all attributes (0x0000-0xffff) will be requested.

ServiceRecords to be registered with the local sdpd(8) server should consist of a list of attribute ID/value pairs, where the attribute ID is a 16-bit unsigned integer element, and the attribute value is any data element. The attribute IDs should be in ascending order, and the first one must be `SDP_ATTR_SERVICE_RECORD_HANDLE` (0x0000), otherwise the server will reject the record. For consistency, records should also contain a BrowseGroupList with the PublicBrowseGroup UUID, plus at least a ServiceName string in the native language with an associated LanguageBaseAttributeIDList although this is not currently enforced.

# FUNCTIONS

`sdp_open`(laddr, raddr)
  Open a SDP session to a remote Bluetooth device. laddr refers to the local bluetooth device address and may be `NULL` in which case it will default to `BDADDR_ANY`.
`sdp_open_local`(control)
  Open a SDP session to a server using a local socket. The control socket path may be given as `NULL` in which case the default control path /var/run/sdp will be used.
`sdp_close`(ss)
  Close SDP session and release all resources.
`sdp_service_search`(ss, ssp, handlep, num)
  Perform a complete ServiceSearch transaction on the SDP session. At most num service record handles matching the ServiceSearchPattern ssp will be returned in the array pointed to by handlep.
`sdp_service_attribute`(ss, handle, ail, response)
  Perform a complete ServiceAttribute transaction on the SDP session. The ServiceRecord with ServiceRecordHandle handle will be parsed using the AttributeIDList ail. If the transaction succeeds, the response data buffer will contain a validated data element list of attribute ID/value pairs from the selected record.
`sdp_service_search_attribute`(ss, ssp, ail, response)
  Perform a complete ServiceSearchAttribute transaction on the SDP session. All ServiceRecords matching the ServiceSearchPattern ssp will be parsed using the AttributeIDList ail. If the transaction succeeds, the response data buffer will contain a valid data element list of sequences, where each sequence is the attribute ID/value list from a matched record.
`sdp_record_insert`(ss, bdaddr, handlep, record)
  Insert a ServiceRecord record. If bdaddr is given, the service record will be restricted to clients connecting through the Bluetooth controller with that BD_ADDR. When the handlep pointer is non NULL, the resulting ServiceRecordHandle will be written to the address given. The record will be valid while the session is active and will be purged when the session is closed.
`sdp_record_update`(ss, handle, record)
  Update a ServiceRecord that is owned by this session. handle is the identifier returned by the `sdp_record_insert`() call, and record is the updated ServiceRecord as described above.
`sdp_record_remove`(ss, handle)
  Remove a ServiceRecord owned by this session. handle is the identifier returned by the `sdp_record_insert`() call.

A single response buffer is maintained for each session, so the results of a ServiceAttribute or ServiceSearchAttribute request will only be valid until another request is made or the session is closed. The SDP specifications do not mandate a limit on the size of the response buffer but this implementation has a default limit of UINT16_MAX bytes. This limit can be increased at runtime by setting the environment variable `SDP_RESPONSE_MAX` to a numeric value.

Records are only allowed to be removed or updated by the session that inserted them, and records will be removed automatically when the session is closed. Further, manipulating service records will normally only be possible for privileged users on a SDP session connected with a local socket. See sdpd(8) and your local system administrator for details.

# RETURN VALUES

Session open routines will return a session handle on success and `NULL` on failure. For service lookup and record manipulation routines, a boolean value is returned indicating success or failure. On failure, errno will be set to indicate the error.

# FILES

/var/run/sdp

# ERRORS

In addition to errors returned by the standard C library IO functions, the following errors may be detected by `libbluetooth`:

[`EINVAL`]
  A provided function argument was not valid.
[`EIO`]
  A response from the remote server was not understood.
[`ENOATTR`]
  The record handle did not exist on the server.

# SEE ALSO

sdpquery(1), bluetooth(3), sdp_data(3), sdpd(8)

The "Service Discovery Protocol" section of the Bluetooth Core specifications, available at http://www.bluetooth.com/

# HISTORY

The first Service Discovery implementation was written for FreeBSD and was ported to NetBSD 4.0. This, the second version API, was designed by Iain Hibbert for NetBSD 6.0 in order to simplify the sdpd(8) daemon and allow client code greater control over all aspects of the service records. The original API is still available when `SDP_COMPAT` is defined but will eventually be removed.

October 13, 2024 | NetBSD 11.0