WlanEnumInterfaces function (wlanapi.h)

Article
10/13/2021

The WlanEnumInterfaces function enumerates all of the wireless LAN interfaces currently enabled on the local computer.

Syntax

DWORD WlanEnumInterfaces(
  [in]  HANDLE                    hClientHandle,
  [in]  PVOID                     pReserved,
  [out] PWLAN_INTERFACE_INFO_LIST *ppInterfaceList
);

Parameters

[in] hClientHandle

The client's session handle, obtained by a previous call to the WlanOpenHandle function.

[in] pReserved

Reserved for future use. This parameter must be set to NULL.

[out] ppInterfaceList

A pointer to storage for a pointer to receive the returned list of wireless LAN interfaces in a WLAN_INTERFACE_INFO_LIST structure.

The buffer for the WLAN_INTERFACE_INFO_LIST returned is allocated by the WlanEnumInterfaces function if the call succeeds.

Return value

If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value may be one of the following return codes.

Return code	Description
ERROR_INVALID_PARAMETER	A parameter is incorrect. This error is returned if the hClientHandle or ppInterfaceList parameter is NULL. This error is returned if the pReserved is not NULL. This error is also returned if the hClientHandle parameter is not valid.
ERROR_INVALID_HANDLE	The handle hClientHandle was not found in the handle table.
RPC_STATUS	Various error codes.
ERROR_NOT_ENOUGH_MEMORY	Not enough memory is available to process this request and allocate memory for the query results.

Remarks

The WlanEnumInterfaces function allocates memory for the list of returned interfaces that is returned in the buffer pointed to by the ppInterfaceList parameter when the function succeeds. The memory used for the buffer pointed to by ppInterfaceList parameter should be released by calling the WlanFreeMemory function after the buffer is no longer needed.

Examples

The following example enumerates the wireless LAN interfaces on the local computer and prints values from the retrieved WLAN_INTERFACE_INFO_LIST structure and the enumerated WLAN_INTERFACE_INFO structures.

Note This example will fail to load on Windows Server 2008 and Windows Server 2008 R2 if the Wireless LAN Service is not installed and started.

#ifndef UNICODE
#define UNICODE
#endif

#include <windows.h>
#include <wlanapi.h>
#include <objbase.h>
#include <wtypes.h>

#include <stdio.h>
#include <stdlib.h>

// Need to link with Wlanapi.lib and Ole32.lib
#pragma comment(lib, "wlanapi.lib")
#pragma comment(lib, "ole32.lib")

int wmain()
{

    // Declare and initialize variables.

    HANDLE hClient = NULL;
    DWORD dwMaxClient = 2;   //    
    DWORD dwCurVersion = 0;
    DWORD dwResult = 0;
    int iRet = 0;
    
    WCHAR GuidString[40] = {0};
     
    int i;

    /* variables used for WlanEnumInterfaces  */
    
    PWLAN_INTERFACE_INFO_LIST pIfList = NULL;
    PWLAN_INTERFACE_INFO pIfInfo = NULL;

    
    dwResult = WlanOpenHandle(dwMaxClient, NULL, &dwCurVersion, &hClient); 
    if (dwResult != ERROR_SUCCESS)  {
        wprintf(L"WlanOpenHandle failed with error: %u\n", dwResult);
        // FormatMessage can be used to find out why the function failed
        return 1;
    }
    
    dwResult = WlanEnumInterfaces(hClient, NULL, &pIfList); 
    if (dwResult != ERROR_SUCCESS)  {
        wprintf(L"WlanEnumInterfaces failed with error: %u\n", dwResult);
        // FormatMessage can be used to find out why the function failed
        return 1;
    }
    else {
        wprintf(L"Num Entries: %lu\n", pIfList->dwNumberOfItems);
        wprintf(L"Current Index: %lu\n", pIfList->dwIndex);
        for (i = 0; i < (int) pIfList->dwNumberOfItems; i++) {
            pIfInfo = (WLAN_INTERFACE_INFO *) &pIfList->InterfaceInfo[i];
            wprintf(L"  Interface Index[%d]:\t %lu\n", i, i);
            iRet = StringFromGUID2(pIfInfo->InterfaceGuid, (LPOLESTR) &GuidString, 39); 
            // For c rather than C++ source code, the above line needs to be
            // iRet = StringFromGUID2(&pIfInfo->InterfaceGuid, (LPOLESTR) &GuidString, 39); 
            if (iRet == 0)
                wprintf(L"StringFromGUID2 failed\n");
            else {
                wprintf(L"  InterfaceGUID[%d]: %ws\n",i, GuidString);
            }    
            wprintf(L"  Interface Description[%d]: %ws", i, 
                pIfInfo->strInterfaceDescription);
            wprintf(L"\n");
            wprintf(L"  Interface State[%d]:\t ", i);
            switch (pIfInfo->isState) {
            case wlan_interface_state_not_ready:
                wprintf(L"Not ready\n");
                break;
            case wlan_interface_state_connected:
                wprintf(L"Connected\n");
                break;
            case wlan_interface_state_ad_hoc_network_formed:
                wprintf(L"First node in a ad hoc network\n");
                break;
            case wlan_interface_state_disconnecting:
                wprintf(L"Disconnecting\n");
                break;
            case wlan_interface_state_disconnected:
                wprintf(L"Not connected\n");
                break;
            case wlan_interface_state_associating:
                wprintf(L"Attempting to associate with a network\n");
                break;
            case wlan_interface_state_discovering:
                wprintf(L"Auto configuration is discovering settings for the network\n");
                break;
            case wlan_interface_state_authenticating:
                wprintf(L"In process of authenticating\n");
                break;
            default:
                wprintf(L"Unknown state %ld\n", pIfInfo->isState);
                break;
            }
            wprintf(L"\n");
        }
    }

    if (pIfList != NULL) {
        WlanFreeMemory(pIfList);
        pIfList = NULL;
    }
    return 0;
}

Requirements

Requirement	Value
Minimum supported client	Windows Vista, Windows XP with SP3 [desktop apps only]
Minimum supported server	Windows Server 2008 [desktop apps only]
Target Platform	Windows
Header	wlanapi.h (include Wlanapi.h)
Library	Wlanapi.lib
DLL	Wlanapi.dll
Redistributable	Wireless LAN API for Windows XP with SP2

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