C++程序中使用Windows系统Native Wifi API的基本教程

Z时代
2024-01-10
分类：综合

Windows应用想要实现连接wifi，监听wifi信号，断开连接等功能，用NativeWifi API是个不错的选择。

打开MSDN,搜索NativeWifi Api，找到Native Wifi页。在这里。

信息量很大，如果像我着急实现上述功能，看海量的文档有些来不及。如果直接给我例子，在运行中调试，阅读代码，效率会更高。

但是，我并没有成功。首先，Sample在SDK中，参见这里。我下载几次都失败了，最后放弃这条路。后来同事给了我一份Sample，我不敢确定是否就是这个，但是代码写的也是很晦涩。我的初衷是简单的使用这些API的例子。

看来还是自己动手吧。看相关API，如果不懂，就找有经验人的例子。

几经周折，终于实现我的需求。让我慢慢道来。

1.获得可用AP列表

参见WlanGetAvailableNetworkList的官方文档，下面有例子。


DWORD WINAPI WlanGetAvailableNetworkList( 
 _In_  HANDLE hClientHandle, 
 _In_  const GUID *pInterfaceGuid, 
 _In_  DWORD dwFlags, 
 _Reserved_ PVOID pReserved, 
 _Out_  PWLAN_AVAILABLE_NETWORK_LIST *ppAvailableNetworkList 
);

由可用列表便可以找到当前哪个AP正在连接，并显示信号强度。

2.监听当前连接

在获得可用AP列表的基础上，遍历当前AP，看谁正在连接，并取得它的信号。代码片段如下：


bool isConnect = false; 
int numberOfItems = pWLAN_AVAILABLE_NETWORK_LIST->dwNumberOfItems; 
  for(int i = 0; i <= numberOfItems; i++) 
  { 
   WLAN_AVAILABLE_NETWORK wlanAN = pWLAN_AVAILABLE_NETWORK_LIST->Network[i]; 
   if(wlanAN.dwFlags & WLAN_AVAILABLE_NETWORK_CONNECTED) 
   { 
    Wprintf(WLAN signal is %s:%d\n", wlanAN.strProfileName, wlanAN.wlanSignalQuality); 
    isConnect = true;     
   } 
  } 
  if(!isConnect){    
 wprintf("Wifi is disconnected!\n");}

3.断开连接

如果wifi处于连接状态，将其断开。WlanDisconnect还是容易使用的。原型如下：


DWORD WINAPI WlanDisconnect( 
 _In_  HANDLE hClientHandle, 
 _In_  const GUID *pInterfaceGuid, 
 _Reserved_ PVOID pReserved 
);

代码演示在后面。

4.连接一个有profile的AP（已保存过密码）

这是本文的重点。

虽然连接函数WlanConnect原型很简单：


DWORD WINAPI WlanConnect( 
 _In_  HANDLE hClientHandle, 
 _In_  const GUID *pInterfaceGuid, 
 _In_  const PWLAN_CONNECTION_PARAMETERS pConnectionParameters, 
 _Reserved_ PVOID pReserved 
);

但参数PWLAN_CONNECTION_PARAMETERS却是很复杂，只要有一个配错，连接就会失败。

还好我的需求还是蛮简单的，只要连接已有的profile的AP。那么我的工作就会有针对性的开展。挫折了好多天，每次都连接失败，原因是ERROR_INVALID_PARAMETER。

就在今天，我终于成功了。真是会者不难，难者不会啊。

看看连接参数的结构体：


typedef struct _WLAN_CONNECTION_PARAMETERS { 
 WLAN_CONNECTION_MODE wlanConnectionMode; 
 LPCWSTR    strProfile; 
 PDOT11_SSID   pDot11Ssid; 
 PDOT11_BSSID_LIST pDesiredBssidList; 
 DOT11_BSS_TYPE  dot11BssType; 
 DWORD    dwFlags; 
} WLAN_CONNECTION_PARAMETERS, *PWLAN_CONNECTION_PARAMETERS;

为了实现我的要求，可以这样赋值：

wlanConnectionMode这里设成wlan_connection_mode_profile；

strProfile写上你要连接ap的名称（通常是profile名称）；

pDot11Ssid用不上，设置NULL；

pDesiredBssidList同样置成NULL；

dot11BssType我给设成dot11_BSS_type_infrastructure（基础设施？）；

dwFlags设置为WLAN_CONNECTION_HIDDEN_NETWORK。

确实是工作了，strProfile如何获取呢？参见监听连接信号中对可用AP列表中第一个profile的获取。

完整代码如下：


// 
#include "stdafx.h" 
#include <windows.h> 
#include <wlanapi.h> 
#include <objbase.h> 
#include <wtypes.h> 
#include <string> 
#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") 
using namespace std; 
int listenStatus() 
{ 
 HANDLE hClient = NULL; 
 DWORD dwMaxClient = 2;   
 DWORD dwCurVersion = 0; 
 DWORD dwResult = 0; 
 DWORD dwRetVal = 0; 
 int iRet = 0; 
 WCHAR GuidString[39] = {0}; 
 //Listen the status of the AP you connected. 
 while(1){ 
  Sleep(5000); 
  PWLAN_INTERFACE_INFO_LIST pIfList = NULL;//I think wlan interface means network card 
  PWLAN_INTERFACE_INFO pIfInfo = NULL; 
  DWORD dwFlags = 0;   
  dwResult = WlanOpenHandle(dwMaxClient, NULL, &dwCurVersion, &hClient); 
  if (dwResult != ERROR_SUCCESS) { 
   wprintf(L"WlanOpenHandle failed with error: %u\n", dwResult); 
   return 1; 
  } 
  dwResult = WlanEnumInterfaces(hClient, NULL, &pIfList); 
  if (dwResult != ERROR_SUCCESS) { 
   wprintf(L"WlanEnumInterfaces failed with error: %u\n", dwResult); 
   return 1; 
  } else { 
   wprintf(L"WLAN_INTERFACE_INFO_LIST for this system\n"); 
   wprintf(L"Num Entries: %lu\n", pIfList->dwNumberOfItems); 
   wprintf(L"Current Index: %lu\n\n", pIfList->dwIndex); 
   int i; 
   for (i = 0; i < (int) pIfList->dwNumberOfItems; i++) { 
    pIfInfo = (WLAN_INTERFACE_INFO *) &pIfList->InterfaceInfo[i]; 
    wprintf(L" Interface Index[%u]:\t %lu\n", i, i); 
    iRet = StringFromGUID2(pIfInfo->InterfaceGuid, (LPOLESTR) &GuidString, 
     sizeof(GuidString)/sizeof(*GuidString)); 
    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; 
    } 
   } 
  } 
 } 
} 
int _tmain(int argc, _TCHAR* argv[]) 
{ 
 HANDLE hClient = NULL; 
 DWORD dwMaxClient = 2;   
 DWORD dwCurVersion = 0; 
 DWORD dwResult = 0; 
 DWORD dwRetVal = 0; 
 int iRet = 0;  
 /* variables used for WlanEnumInterfaces */ 
 PWLAN_INTERFACE_INFO_LIST pIfList = NULL; 
 PWLAN_INTERFACE_INFO pIfInfo = NULL; 
 LPCWSTR pProfileName = NULL; 
 LPWSTR pProfileXml = NULL; 
 DWORD dwFlags = 0; 
 pProfileName = argv[1]; 
 wprintf(L"Information for profile: %ws\n\n", pProfileName); 
 dwResult = WlanOpenHandle(dwMaxClient, NULL, &dwCurVersion, &hClient); 
 if (dwResult != ERROR_SUCCESS) { 
  wprintf(L"WlanOpenHandle failed with error: %u\n", dwResult); 
  return 1; 
 } 
 dwResult = WlanEnumInterfaces(hClient, NULL, &pIfList); 
 if (dwResult != ERROR_SUCCESS) { 
  wprintf(L"WlanEnumInterfaces failed with error: %u\n", dwResult); 
  return 1; 
 } else { 
  dwResult = WlanDisconnect(hClient, &pIfList->InterfaceInfo[0].InterfaceGuid,NULL);//DISCONNECT FIRST 
  if(dwResult != ERROR_SUCCESS) 
  { 
   printf("WlanDisconnect failed with error: %u\n",dwResult); 
   return -1; 
  } 
  PWLAN_AVAILABLE_NETWORK_LIST pWLAN_AVAILABLE_NETWORK_LIST = NULL; 
  dwResult = WlanGetAvailableNetworkList(hClient, &pIfList->InterfaceInfo[0].InterfaceGuid, 
    WLAN_AVAILABLE_NETWORK_INCLUDE_ALL_MANUAL_HIDDEN_PROFILES, 
    NULL, &pWLAN_AVAILABLE_NETWORK_LIST); 
  if (dwResult != ERROR_SUCCESS) 
  {    
   printf("WlanGetAvailableNetworkList failed with error: %u\n",dwResult); 
   WlanFreeMemory(pWLAN_AVAILABLE_NETWORK_LIST); 
   return -1; 
  } 
  WLAN_AVAILABLE_NETWORK wlanAN = pWLAN_AVAILABLE_NETWORK_LIST->Network[0];//PLEASE CHECK THIS YOURSELF 
  if(pProfileName == NULL) 
   pProfileName = wlanAN.strProfileName;  
  WLAN_CONNECTION_PARAMETERS wlanConnPara; 
  wlanConnPara.wlanConnectionMode =wlan_connection_mode_profile ; //YES,WE CONNECT AP VIA THE PROFILE 
  wlanConnPara.strProfile =pProfileName;       // set the profile name 
  wlanConnPara.pDot11Ssid = NULL;         // SET SSID NULL 
  wlanConnPara.dot11BssType = dot11_BSS_type_infrastructure;  //dot11_BSS_type_any,I do not need it this time.   
  wlanConnPara.pDesiredBssidList = NULL;       // the desired BSSID list is empty 
  wlanConnPara.dwFlags = WLAN_CONNECTION_HIDDEN_NETWORK;   //it works on my WIN7\8 
  dwResult=WlanConnect(hClient,&pIfList->InterfaceInfo[0].InterfaceGuid,&wlanConnPara ,NULL); 
  if (dwResult==ERROR_SUCCESS) 
  { 
   printf("WlanConnect success!\n"); 
  } 
  else 
  { 
   printf("WlanConnect failed err is %d\n",dwResult); 
  } 
 } 
 listenStatus(); //LISTEN THE STATUS 
 if (pProfileXml != NULL) { 
  WlanFreeMemory(pProfileXml); 
  pProfileXml = NULL; 
 } 
 if (pIfList != NULL) { 
  WlanFreeMemory(pIfList); 
  pIfList = NULL; 
 } 
 return dwRetVal; 
}

5.打开网络设置界面

遇到以前没有连接过的AP，需要输入密码，那么，直接打开配置界面让用户自己来搞吧。


ShellExecute( 
 NULL, 
 L"open", 
 L"shell:::{21EC2020-3AEA-1069-A2DD-08002B30309D}\\::{38a98528-6cbf-4ca9-8dc0-b1e1d10f7b1b}", 
 NULL, 
 NULL, 
 SW_SHOWNORMAL);

6.RSSI

当屏幕上打印出“WlanConnect success!”的时候，别提多高兴了。

就像爱迪生试验灯丝一下，在无数次失败后，终于找到了一种材料可以胜任灯丝的工作。这种喜悦真的令人振奋，往日的阴霾和不爽终于一扫而光。

其实我也尝试过WlanGetProfile和WlanSetProfile，虽然有时结果是能够连上指定AP，但是函数返回结果却总是ERROR_INVALID_PARAMETER。

网上的例子，很多都是抄来抄去的，写的不明不白，虽然有过帮助，但是也有些误导。

今天自己成功的连接到指定AP了（用命令行运行我的例子，输入参数profile name），我一定要把它发表出来，让其他人有个参考。

我认为这是一件诚意的作品，在此也谢谢给过我帮助的朋友。

最后说一下获得的信号。标准信号RSSI是负值，而这里获得的信号都是正值（0~100），在有些需要RSSI的地方，我们需要转换一下：


if (pBssEntry->wlanSignalQuality == 0) 
  iRSSI = -100; 
 else if (pBssEntry->wlanSignalQuality == 100)  
  iRSSI = -50; 
 else 
  iRSSI = -100 + (pBssEntry->wlanSignalQuality/2);  
 wprintf(L" Signal Quality[%u]:\t %u (RSSI: %i dBm)\n", j, 
  pBssEntry->wlanSignalQuality, iRSSI);

7.Wifi on与wifi off

下面要说的是在软件层面控制无线网卡的开和关。

问题听起来简单，调查起来复杂，但解决起来却也简单。关键函数便是Native wifi api中的WlanSetInterface。其实这个API功能也是非

常强大的，我只用到其中控制wifi radio state的功能。官网文档在此。

函数原型：


DWORD WINAPI WlanSetInterface( 
 _In_  HANDLE hClientHandle, 
 _In_  const GUID *pInterfaceGuid, 
 _In_  WLAN_INTF_OPCODE OpCode, 
 _In_  DWORD dwDataSize, 
 _In_  const PVOID pData, 
 _Reserved_ PVOID pReserved 
);

重点说一下三个参数：

（1） OpCode，指定要设置的参数。我们选择wlan_intf_opcode_radio_state

（2） DwDataSize，pData的size。传入时用sizeof得到。

（3） pData，radio state对应的data是WLAN_PHY_RADIO_STATE。

看看这个state结构体：


typedef struct _WLAN_PHY_RADIO_STATE { 
 DWORD    dwPhyIndex; 
 DOT11_RADIO_STATE dot11SoftwareRadioState; 
 DOT11_RADIO_STATE dot11HardwareRadioState; 
} WLAN_PHY_RADIO_STATE, *PWLAN_PHY_RADIO_STATE;

Index设为0.

State设置如下：

typedef enum _DOT11_RADIO_STATE {

dot11_radio_state_unknown,

dot11_radio_state_on,

dot11_radio_state_off

} DOT11_RADIO_STATE, *PDOT11_RADIO_STATE;

与前几个API（比如wlanconnect）相比，这个函数的使用简单多了。全部源码如下：


// ManageWirelessNetwork.cpp : Defines the entry point for the console application. 
// 
#include "stdafx.h" 
#include <stdio.h> 
#include <windows.h> 
#include <shellapi.h> 
#include <wlanapi.h> 
// Need to link with shell32.lib 
#pragma comment(lib, "shell32.lib") 
#pragma comment(lib, "wlanapi.lib") 
int _tmain(int argc, _TCHAR* argv[]) 
{ 
 DWORD dwResult = 0; 
 DWORD dwMaxClient = 2; 
 DWORD dwCurVersion = 0; 
 HANDLE hClient = NULL; 
 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); 
  return false; 
 } 
 dwResult = WlanEnumInterfaces(hClient, NULL, &pIfList); 
 if (dwResult != ERROR_SUCCESS) { 
  wprintf(L"WlanEnumInterfaces failed with error: %u\n", dwResult); 
  return false; 
 } 
 WLAN_PHY_RADIO_STATE state; 
 state.dwPhyIndex = 0; 
 state.dot11SoftwareRadioState = dot11_radio_state_on; 
 PVOID pData = &state; 
 dwResult = WlanSetInterface(hClient,&pIfList->InterfaceInfo[0].InterfaceGuid, 
  wlan_intf_opcode_radio_state,sizeof(WLAN_PHY_RADIO_STATE),pData,NULL); 
 if(dwResult == ERROR_SUCCESS) 
 { 
  wprintf(L"set state success!\n"); 
 } 
 else 
 { 
  wprintf(L"set state failed!err is %d\n",dwResult); 
 } 
 return 0; 
}

8.GOTO在释放资源时的作用

GOTO语句有着很臭的名声，我们的老师经常教导我们说，不要轻易使用它。

C++跳转语句有三个：goto、break和continue。它们只是工具，我觉得问题不能归咎于工具，问题在于人。

就像指针一样，goto这个无条件跳转语句力量还是很强大的，如果滥用，出现问题很难排查。

但有些时候goto确实是不二选择，例如我遇到的，在函数中有多个出口，而每个出口都遇到释放资源的时候，与其都把释放语句不厌其烦的写一遍，

不如一个goto语句来的干脆利落。

下面的例子取自上一篇Native Wifi API文章，由于我们的程序经常控制的wifi的on和off，必须注意释放资源。就拿WlanOpenHandle来说，

如果不注意对称WlanCloseHandler，程序几次运行后报错：ERROR_REMOTE_SESSION_LIMIT_EXCEEDED

官网解释为：Too many handles have been issued by the server.

所以我们会在每个API调用后，确认返回值，如果错误，程序将不再继续向下运行，return之前，我们必须释放资源。当出口很多时，我们要写很多同样的代码，

很烦躁，难读，代码急速膨胀。但使用goto后，问题便轻松了许多，请看简单例子：


// ManageWirelessNetwork.cpp : Defines the entry point for the console application. 
// 
#include "stdafx.h" 
#include <stdio.h> 
#include <windows.h> 
#include <shellapi.h> 
#include <wlanapi.h> 
// Need to link with shell32.lib 
#pragma comment(lib, "shell32.lib") 
#pragma comment(lib, "wlanapi.lib") 
int _tmain(int argc, _TCHAR* argv[]) 
{ 
  DWORD dwResult = 0; 
  DWORD dwMaxClient = 2; 
  DWORD dwCurVersion = 0; 
  HANDLE hClient = NULL; 
  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); 
    return false; 
  } 
  dwResult = WlanEnumInterfaces(hClient, NULL, &pIfList); 
  if (dwResult != ERROR_SUCCESS) { 
    wprintf(L"WlanEnumInterfaces failed with error: %u\n", dwResult); 
    goto RELEASE_RESOURCE; 
  } 
  WLAN_PHY_RADIO_STATE state; 
  state.dwPhyIndex = 0; 
  state.dot11SoftwareRadioState = dot11_radio_state_on;//off here too. 
  PVOID pData = &state; 
  dwResult = WlanSetInterface(hClient,&pIfList->InterfaceInfo[0].InterfaceGuid, 
    wlan_intf_opcode_radio_state,sizeof(WLAN_PHY_RADIO_STATE),pData,NULL); 
  if(dwResult == ERROR_SUCCESS) 
  { 
    wprintf(L"set state success!\n"); 
  } 
  else 
  { 
    wprintf(L"set state failed!err is %d\n",dwResult); 
  } 
RELEASE_RESOURCE: 
  if(hClient) 
  { 
    WlanCloseHandle(hClient,NULL); 
    hClient = NULL; 
  } 
  if(pIfList) 
  { 
    WlanFreeMemory(pIfList); 
    pIfList = NULL; 
  } 
  if(pIfInfo) 
  { 
    WlanFreeMemory(pIfInfo); 
    pIfInfo = NULL; 
  } 
  return 0; 
}