WSALookupServiceBegin (Windows Sockets)

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

This function initiates a client query that is constrained by the information contained within a WSAQUERYSET (Windows Sockets) structure. This function only returns a handle, which should be used by subsequent calls to the WSALookupServiceNext (Windows Sockets) function to get the actual results.

Syntax

INT WSALookupServiceBegin(
  LPWSAQUERYSET lpqsRestrictions,
  DWORD dwControlFlags,
  LPHANDLE lphLookup
);

Parameters

• lpqsRestrictions
  [in] Pointer to the search criteria.

• dwControlFlags
  [in] Flag that controls the depth of the search. The following table shows a list of flags for the dwControlFlags parameter.

  Flag	Description
  LUP_DEEP	Queries deep as opposed to just the first level.
  LUP_NOCONTAINERS	Does not return any containers.
  LUP_NEAREST	If possible, returns results in the order of distance. The measure of distance is provider specific.
  LUP_RES_SERVICE	Indicates whether prime response is in the remote or local part of the CSADDR_INFO structure. The other part needs to be usable in either case.
  LUP_RETURN_ALIASES	Any available alias information is to be returned in successive calls to WSALookupServiceNext (Windows Sockets), and each alias returned will have the RESULT_IS_ALIAS flag set.
  LUP_RETURN_NAME	Retrieves the name as lpszServiceInstanceName.
  LUP_RETURN_TYPE	Retrieves the type as lpServiceClassId.
  LUP_RETURN_VERSION	Retrieves the version as lpVersion.
  LUP_RETURN_COMMENT	Retrieves the comment as lpszComment.
  LUP_RETURN_ADDR	Retrieves the addresses as lpcsaBuffer.
  LUP_RETURN_BLOB	Retrieves the private data as lpBlob.
  LUP_RETURN_ALL	Retrieves all of the information.

• lphLookup
  [out] Handle to be used when calling WSALookupServiceNext (Windows Sockets) to start retrieving the results set.

Return Value

The return value is zero if the operation was successful. If an error occurs, the value SOCKET_ERROR is returned, and a specific error number can be retrieved by calling the WSAGetLastError function.

The following table shows a list of possible error codes.

Remarks

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

Some name service providers can have other means of finding containers. For example, containers might all be of some well-known type, or of a set of well-known types, and therefore a query restriction can 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. Hence, if a query restriction is given that includes containers, specifying LUP_NOCONTAINERS will prevent the container items from being returned. Similarly, no matter the query restriction, if LUP_CONTAINERS is given, only containers should be returned. If a name space does not support containers, and LUP_CONTAINERS is specified, it should simply return WSANO_DATA.

The following code sample is the preferred method of obtaining the containers within another container.

dwStatus = WSALookupServiceBegin(
      lpqsRestrictions,
      LUP_CONTAINERS,
      lphLookup);

This call is followed by the requisite number of WSALookupServiceNext (Windows Sockets) 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 WSALookupServiceBegin use the containers returned from a previous call.

As mentioned above, a WSAQUERYSET (Windows Sockets) structure is used as an input parameter to WSALookupBegin to qualify the query. The following table indicates how the WSAQUERYSET (Windows Sockets) structure is used to construct a query. When a parameter is marked as (Optional), a NULL pointer can be supplied, indicating that the parameter will not be used as a search criteria.

Notes for Bluetooth

Bluetooth clients use WSALookupServiceBegin (Windows Sockets), WSALookupServiceNext (Windows Sockets), and WSALookupServiceEnd to discover the existence of a particular service on the Bluetooth RFCOMM server. Queries can be done for local and remote addresses, although for RFCOMM a client can connect only to remote addresses.

Requirements

See Also

Reference

WSAGetLastError
WSALookupServiceEnd (Windows Sockets)
WSALookupServiceNext (Windows Sockets)
WSAStartup