LPNSPLOOKUPSERVICENEXT callback function (ws2spi.h)

Article
10/13/2021

The NSPLookupServiceNext function is called after obtaining a handle from a previous call to NSPLookupServiceBegin in order to retrieve the requested service information.

The provider will pass a WSAQUERYSET structure in the lpqsResults buffer. The client should call this function until it returns WSA_E_NOMORE, indicating that all the WSAQUERYSET have been returned.

Syntax

LPNSPLOOKUPSERVICENEXT Lpnsplookupservicenext;

INT Lpnsplookupservicenext(
  [in]      HANDLE hLookup,
  [in]      DWORD dwControlFlags,
  [in, out] LPDWORD lpdwBufferLength,
  [out]     LPWSAQUERYSETW lpqsResults
)
{...}

Parameters

[in] hLookup

A handle returned from the previous call to WSALookupServiceBegin.

[in] dwControlFlags

The flags used to control the next operation. Currently, only LUP_FLUSHPREVIOUS is defined as a means to handle a result set that is too large. If an application cannot supply a large enough buffer, setting LUP_FLUSHPREVIOUS instructs the provider to discard the last result set, which was too large, and move to the next set for this call.

[in, out] lpdwBufferLength

The size, in bytes, on input, that is contained in the buffer pointed to by lpqsResults. On output, if the function fails and the error is WSAEFAULT, then it contains the minimum size, in bytes to pass for the lpqsResults to retrieve the record.

[out] lpqsResults

A pointer to a memory block that will contain, on return, one result set in a WSAQUERYSET structure.

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_E_CANCELLED	A call to NSPLookupServiceEnd was made while this call was still processing. The call has been canceled. The data in the lpqsResults buffer is undefined. In Windows Sockets 2, conflicting error codes are defined for WSAECANCELLED (10103) and WSA_E_CANCELLED (10111).The error code WSAECANCELLED will be removed in a future version and only WSA_E_CANCELLED will remain. Namespace providers should use the WSA_E_CANCELLED error code to maintain compatibility with the widest possible range of applications.
WSA_E_NO_MORE	There is no more data available. In Windows Sockets 2, conflicting error codes are defined for WSAENOMORE (10102) and WSA_E_NO_MORE (10110).The error code WSAENOMORE will be removed in a future version and only WSA_E_NO_MORE will remain. Namespace providers should use the WSA_E_NO_MORE error code to maintain compatibility with the widest possible range of applications.
WSA_INVALID_HANDLE	The specified lookup handle is invalid.
WSA_NOT_ENOUGH_MEMORY	There is not enough memory available to perform this operation.
WSAEFAULT	The lpqsResults buffer was too small to contain a WSAQUERYSET set.
WSAEINVAL	One or more parameters are 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 no data, matching the given restrictions, was located.
WSASERVICE_NOT_FOUND	The service is unknown. The service cannot be found in the specified namespace.

Remarks

The dwControlFlags specified in this function and the ones specified at the time of NSPLookupServiceBegin are handled as "restrictions" for the purpose of combination. The restrictions are combined between the ones at NSPLookupServiceBegin time and the ones at NSPLookupServiceNext time. Therefore, the flags at NSPLookupServiceNext can never increase the amount of data returned beyond what was requested at NSPLookupServiceBegin, although it is not an error to specify more or less flags. The flags specified at a given NSPLookupServiceNext apply only to that call.

The dwControlFlags LUP_FLUSHPREVIOUS and LUP_RES_SERVICE are exceptions to the combined restrictions rule (because they are behavior flags instead of "restriction" flags). If either flag is used in NSPLookupServiceNext, they have their defined effect regardless of the setting of the same flags at NSPLookupServiceBegin.

For example, if LUP_RETURN_VERSION is specified at NSPLookupServiceBegin, the service provider retrieves records including the version. If LUP_RETURN_VERSION is not specified at NSPLookupServiceNext, the returned information does not include the version, even though it was available. No error is generated.

Also for example, if LUP_RETURN_BLOB is not specified at NSPLookupServiceBegin, but is specified at NSPLookupServiceNext, the returned information does not include the private data. No error is generated.

Query Results

The following table lists WSAQUERYSET and describes how query results are represented in the WSAQUERYSET structure. For more information, see Query-Related Data Structures.

WSAQUERYSET member name	Result interpretation
dwSize	Will be set to sizeof(WSAQUERYSET). This is used as a versioning mechanism.
dwOutputFlags	RESULT_IS_ALIAS flag indicates this is an alias result.
lpszServiceInstanceName	References the string that contains the service name.
lpServiceClassId	GUID corresponding to the service class.
lpVersion	References version number of the particular service instance.
lpszComment	Optional. Comment string supplied by service instance.
dwNameSpace	Namespace in which the service instance was found.
lpNSProviderId	Identifies the specific namespace provider that supplied this query result.
lpszContext	Specifies the context point in a hierarchical namespace at which the service is located.
dwNumberOfProtocols	Undefined for results.
lpafpProtocols	Undefined for results, all needed protocol information is in the CSADDR_INFO structures.
lpszQueryString	When dwControlFlags includes LUP_RETURN_QUERY_STRING, this member returns the unparsed remainder of the lpszServiceInstanceName specified in the original query. For example, in a namespace that identifies services by hierarchical names that specify a host name and a file path within that host, the address returned might be the host address and the unparsed remainder might be the file path. If the lpszServiceInstanceName is fully parsed and LUP_RETURN_QUERY_STRING is used, this member is null or points to a zero-length string.
dwNumberOfCsAddrs	Indicates the number of elements in the array of CSADDR_INFO structures.
lpcsaBuffer	A pointer to an array of CSADDR_INFO structures, with one complete transport address contained within each element.
lpBlob	Optional. A pointer to a provider-specific entity.

Requirements

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

WSAQUERYSET member name	Result interpretation
dwSize	Will be set to sizeof(WSAQUERYSET). This is used as a versioning mechanism.
dwOutputFlags	RESULT_IS_ALIAS flag indicates this is an alias result.
lpszServiceInstanceName	References the string that contains the service name.
lpServiceClassId	GUID corresponding to the service class.
lpVersion	References version number of the particular service instance.
lpszComment	Optional. Comment string supplied by service instance.
dwNameSpace	Namespace in which the service instance was found.
lpNSProviderId	Identifies the specific namespace provider that supplied this query result.
lpszContext	Specifies the context point in a hierarchical namespace at which the service is located.
dwNumberOfProtocols	Undefined for results.
lpafpProtocols	Undefined for results, all needed protocol information is in the CSADDR_INFO structures.
lpszQueryString	When dwControlFlags includes LUP_RETURN_QUERY_STRING, this member returns the unparsed remainder of the lpszServiceInstanceName specified in the original query. For example, in a namespace that identifies services by hierarchical names that specify a host name and a file path within that host, the address returned might be the host address and the unparsed remainder might be the file path. If the lpszServiceInstanceName is fully parsed and LUP_RETURN_QUERY_STRING is used, this member is null or points to a zero-length string.
dwNumberOfCsAddrs	Indicates the number of elements in the array of CSADDR_INFO structures.
lpcsaBuffer	A pointer to an array of CSADDR_INFO structures, with one complete transport address contained within each element.
lpBlob	Optional. A pointer to a provider-specific entity.

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