LPNSPLOOKUPSERVICEBEGIN callback function (ws2spi.h)

The NSPLookupServiceBegin function initiates a client query of a name service provider that is constrained by the information contained within a WSAQUERYSET structure.

NSPLookupServiceBegin only returns a handle, which should be used by subsequent calls to NSPLookupServiceNext to get the actual results. Because this operation cannot be canceled, it should be implemented to execute quickly. While it is acceptable to initiate a network query, this function should not require a response to return successfully.

Syntax

LPNSPLOOKUPSERVICEBEGIN Lpnsplookupservicebegin;

INT Lpnsplookupservicebegin(
  LPGUID lpProviderId,
  LPWSAQUERYSETW lpqsRestrictions,
  LPWSASERVICECLASSINFOW lpServiceClassInfo,
  DWORD dwControlFlags,
  LPHANDLE lphLookup
)
{...}

Parameters

lpProviderId

A pointer to the name service provider identifier to query.

lpqsRestrictions

A pointer to the search criteria. See Remarks.

lpServiceClassInfo

A pointer to the WSASERVICECLASSINFO structure that contains schema information for the service.

dwControlFlags

A value that controls the depth of the search.

Value Meaning
LUP_DEEP
0x0001
Queries down the hierarchy of a provider as opposed to just the first level.
LUP_CONTAINERS
0x0002
Returns containers only.
LUP_NOCONTAINERS
0x0004
Returns no containers.
LUP_NEAREST
0x0008
If possible, returns results in the order of distance. The measure of distance is provider specific.
LUP_RETURN_NAME
0x0010
Retrieves the name as **lpszServiceInstanceName**.
LUP_RETURN_TYPE
0x0020
Retrieves the type as **lpServiceClassId**.
LUP_RETURN_VERSION
0x0040
Retrieves the version as **lpVersion**.
LUP_RETURN_COMMENT
0x0080
Retrieves the comment as **lpszComment**.
LUP_RETURN_ADDR
0x0100
Retrieves the addresses as **lpcsaBuffer**.
LUP_RETURN_BLOB
0x0200
Retrieves the private data as **lpBlob**.
LUP_RETURN_ALIASES
0x0400
Any available alias information is to be returned in successive calls to NSPLookupServiceNext, and each alias returned will have the **RESULT_IS_ALIAS** flag set.
LUP_RETURN_QUERY_STRING
0x0800
Retrieves the query string as **lpszQueryString**.
LUP_RETURN_ALL
0x0ff0
Retrieves information including the name, type, version, comment, address, blob, aliases, and query string.
LUP_FLUSHCACHE
0x1000
If the provider has cached information, ignore the cache and query the namespace itself.
LUP_FLUSHPREVIOUS
0x2000
Used as a value for the dwControlFlags parameter in NSPLookupServiceNext. Setting this flag instructs the provider to discard the last result set, which was too large for the supplied buffer, and move on to the next result set.
LUP_NON_AUTHORITATIVE
0x4000
Indicates that the namespace provider should included non-authoritative results for names.
LUP_RES_RESERVICE
0x8000
Indicates whether prime response is in the remote or local part of CSADDR_INFO structure. The other part must be usable in either case. This option applies only to service instance requests.
LUP_SECURE
0x8000
Indicates that the namespace provider should use a secure query. This option only applies to name query requests.
LUP_RETURN_PREFERRED_NAMES
0x10000
Indicates that the namespace provider should return only preferred names.
LUP_ADDRCONFIG
0x100000
Indicates that the namespace provider should return the address configuration.
LUP_DUAL_ADDR
0x200000
Indicates that the namespace provider should return the dual addresses. This option only applies to dual-mode sockets (IPv6 and IPv4 mapped addresses).

lphLookup

A pointer to the handle to be used in subsequent calls to NSPLookupServiceNext in order to retrieve the results set.

Return value

The function should return NO_ERROR (zero) if the routine succeeds. It should return SOCKET_ERROR (–1) if the routine fails and it must set the appropriate error code using WSASetLastError.

Error code Meaning
WSA_NOT_ENOUGH_MEMORY
There is not enough memory available to perform this operation.
WSAEINVAL
One or more parameters were invalid, or missing, for this provider.
WSAEOPNOTSUPP
The operation is not supported. This error is returned if the namespace provider does not implement this function.
WSANO_DATA
The name was found in the database, but it does not have the correct associated data that is resolved for.
WSASERVICE_NOT_FOUND
Service is unknown. The service cannot be found in the specified namespace.

Remarks

If LUP_CONTAINERS is specified in a call, avoid all other restriction values. If any are supplied, the name service provider must decide if it can support this restriction over the containers. If not, it should return an error.

Some name service providers may have other means of finding containers. For example, containers can all be of some well-known type, or of a set of well-known types, and therefore a query restriction could be created for finding them. No matter what other means the name service provider has for locating containers, LUP_CONTAINERS and LUP_NOCONTAINERS take precedence. Therefore, if a query restriction is given that includes containers, specifying LUP_NOCONTAINERS will prevent the container items from being returned. Similarly, no matter what the query restriction, if LUP_CONTAINERS is given, only containers should be returned. If a namespace does not support containers and LUP_CONTAINERS is specified, it should return WSANO_DATA.

The preferred method of obtaining the containers within another container, is the call:

dwStatus = NSPLookupServiceBegin(
    lpqsRestrictions,
    LUP_CONTAINERS,
    lphLookup);

followed by the requisite number of NSPLookupServiceNext calls. This will return all containers contained immediately within the starting context; that is, it is not a deep query. With this, one can map the address space structure by walking the hierarchy, perhaps enumerating the content of selected containers. Subsequent uses of NSPLookupServiceBegin use the containers returned from a previous call.

Forming Queries

As mentioned, a WSAQUERYSET structure is used as an input parameter to NSPLookupServiceBegin to qualify the query. The following table lists WSAQUERYSET member names and describes how the WSAQUERYSET is used to construct a query. When a member is marked as (Optional) a null pointer can be supplied, indicating that the parameter will not be used as a search criteria. For more information, see Query-Related Data Structures.

WSAQUERYSET member name Query interpretation
**dwSize** Will be set to sizeof(WSAQUERYSET). This is a versioning mechanism.
**dwOutputFlags** Ignored for queries.
**lpszServiceInstanceName** Optional. Referenced string contains service name. The semantics for wildcarding within the string are not defined, but can be supported by certain namespace providers.
**lpServiceClassId** Required. GUID corresponding to the service class.
**lpVersion** Optional. References desired version number and provides version comparison semantics (that is, version must match exactly, or version must be not less than the value supplied).
**lpszComment** Ignored for queries.
**dwNameSpace** Identifier of a single namespace in which to constrain the search, or **NS_ALL** to include all namespaces.
**lpNSProviderId** Optional. References the GUID of a specific namespace provider and limits the query to this provider only.
**lpszContext** Optional. Specifies the starting point of the query in a hierarchical namespace.
**dwNumberOfProtocols** Size, in bytes, of the number of entries in the protocol constraint array, can be zero.
**lpafpProtocols** Optional. A references to an array of AFPROTOCOLS structures. Only services that use these protocols will be returned. It is permissable for the value **AF_UNSPEC** to appear as a protocol family value, signifying a wildcard. Namespace providers may supply information about any service that uses the corresponding protocol, regardless of address family.
**lpszQueryString** Optional. Some namespaces (such as whois++) support rich SQL-like queries contained in a simple text string. This parameter is used to specify that string.
**dwNumberOfCsAddrs** Ignored for queries.
**lpcsaBuffer** Ignored for queries.
**lpBlob** Optional. A pointer to a provider-specific entity.

Requirements

   
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header ws2spi.h

See also

AFPROTOCOLS

NSPLookupServiceEnd

NSPLookupServiceNext

NSP_ROUTINE

WSAQUERYSET

WSASERVICECLASSINFO

WSASetLastError