WNetOpenEnumA function (winnetwk.h)

Article
02/09/2023

The WNetOpenEnum function starts an enumeration of network resources or existing connections. You can continue the enumeration by calling the WNetEnumResource function.

Syntax

DWORD WNetOpenEnumA(
  [in]  DWORD          dwScope,
  [in]  DWORD          dwType,
  [in]  DWORD          dwUsage,
  [in]  LPNETRESOURCEA lpNetResource,
  [out] LPHANDLE       lphEnum
);

Parameters

[in] dwScope

Scope of the enumeration. This parameter can be one of the following values.

Value	Meaning
RESOURCE_CONNECTED	Enumerate all currently connected resources. The function ignores the dwUsage parameter. For more information, see the following Remarks section.
RESOURCE_CONTEXT	Enumerate only resources in the network context of the caller. Specify this value for a Network Neighborhood view. The function ignores the dwUsage parameter.
RESOURCE_GLOBALNET	Enumerate all resources on the network.
RESOURCE_REMEMBERED	Enumerate all remembered (persistent) connections. The function ignores the dwUsage parameter.

[in] dwType

Resource types to be enumerated. This parameter can be a combination of the following values.

Value	Meaning
RESOURCETYPE_ANY	All resources. This value cannot be combined with RESOURCETYPE_DISK or RESOURCETYPE_PRINT.
RESOURCETYPE_DISK	All disk resources.
RESOURCETYPE_PRINT	All print resources.

If a network provider cannot distinguish between print and disk resources, it can enumerate all resources.

[in] dwUsage

Resource usage type to be enumerated. This parameter can be a combination of the following values.

Value	Meaning
0	All resources.
RESOURCEUSAGE_CONNECTABLE	All connectable resources.
RESOURCEUSAGE_CONTAINER	All container resources.
RESOURCEUSAGE_ATTACHED	Setting this value forces WNetOpenEnum to fail if the user is not authenticated. The function fails even if the network allows enumeration without authentication.
RESOURCEUSAGE_ALL	Setting this value is equivalent to setting RESOURCEUSAGE_CONNECTABLE, RESOURCEUSAGE_CONTAINER, and RESOURCEUSAGE_ATTACHED.

This parameter is ignored unless the dwScope parameter is equal to RESOURCE_GLOBALNET. For more information, see the following Remarks section.

[in] lpNetResource

Pointer to a NETRESOURCE structure that specifies the container to enumerate. If the dwScope parameter is not RESOURCE_GLOBALNET, this parameter must be NULL.

If this parameter is NULL, the root of the network is assumed. (The system organizes a network as a hierarchy; the root is the topmost container in the network.)

If this parameter is not NULL, it must point to a NETRESOURCE structure. This structure can be filled in by the application or it can be returned by a call to the WNetEnumResource function. The NETRESOURCE structure must specify a container resource; that is, the RESOURCEUSAGE_CONTAINER value must be specified in the dwUsage parameter.

To enumerate all network resources, an application can begin the enumeration by calling WNetOpenEnum with the lpNetResource parameter set to NULL, and then use the returned handle to call WNetEnumResource to enumerate resources. If one of the resources in the NETRESOURCE array returned by the WNetEnumResource function is a container resource, you can call WNetOpenEnum to open the resource for further enumeration.

[out] lphEnum

Pointer to an enumeration handle that can be used in a subsequent call to WNetEnumResource.

Return value

If the function succeeds, the return value is NO_ERROR.

If the function fails, the return value is a system error code, such as one of the following values.

Return code	Description
ERROR_NOT_CONTAINER	The lpNetResource parameter does not point to a container.
ERROR_INVALID_PARAMETER	Either the dwScope or the dwType parameter is invalid, or there is an invalid combination of parameters.
ERROR_NO_NETWORK	The network is unavailable.
ERROR_EXTENDED_ERROR	A network-specific error occurred. To obtain a description of the error, call the WNetGetLastError function.
ERROR_INVALID_ADDRESS	A remote network resource name supplied in the NETRESOURCE structure resolved to an invalid network address.

Remarks

If the dwScope parameter is equal to RESOURCE_CONNECTED, a network connection made using the Microsoft LAN Manager network is omitted from the enumeration if the connection was made by an application running in a different logon session than the application calling the WNetOpenEnum function. This is because connections made using Microsoft LAN Manager are visible only to applications running in the same logon session as the application that made the connection. (To include the connection in the enumeration, it is not sufficient for the application to be running in the user account that created the connection.)

The exact interpretation of RESOURCE_CONTEXT in the dwScope parameter depends on the networks installed on the machine.

The WNetOpenEnum function is used to begin enumeration of the resources in a single container. The following examples show the hierarchical structure of a Microsoft LAN Manager network and a Novell NetWare network and identify the containers.

LanMan (container, in this case the provider) 
  ACCOUNTING (container, in this case the domain) 
    \\ACCTSPAY (container, in this case the server) 
      PAYFILES (disk) 
      LASERJET (print) 
 
NetWare (container, in this case the provider) 
  MARKETING (container, in this case the server) 
    SYS (disk, first one on any NetWare server) 
    ANOTHERVOLUME (disk) 
    LASERJET (print)

Examples

For a code sample that illustrates an application-defined function that enumerates all the resources on a network, see Enumerating Network Resources.

Note

The winnetwk.h header defines WNetOpenEnum as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

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	winnetwk.h
Library	Mpr.lib
DLL	Mpr.dll

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