如何检测 WiFi（重新）连接的时间？

Question

抱歉，我没有要显示的代码。这可能会使这个问题成为Programmers 的候选者，但他们在这里没有语言特定领域，我正在寻找德尔福解决方案，所以我会在这里问。我希望这是可以接受的。

基本上，我想在 WiFi 连接时自动启动我的 VPN。我将如何检测到这一点？在这件事上，谷歌似乎不是我的朋友。

Answer 1

所需的 WinApi 调用未在 Delphi 中实现 - 您必须自己定义和调用它们。在这种情况下，相关的功能是：

---

WlanOpenHandle (MSDN)

WlanRegisterNotification (MSDN)

WLAN_NOTIFICATION_SOURCE structure (MSDN)

---

您可以将它们定义为：

const
  wlanapi = 'wlanapi.dll';
  WLAN_NOTIFICATION_SOURCE_ACM = $00000008;

type
  GUID = TGUID;
  HANDLE = THandle;

  PWLanNotificationData = ^TWLanNotificationData;
  TWLanNotificationData = record
    NotificationSource: DWORD;
    NotificationCode: DWORD;
    InterfaceGuid: GUID;
    dwDataSize: DWORD;
    pData: PVOID;
  end;

  TWLanNotificationCallback = procedure(data: PWLanNotificationData; context: PVOID); stdcall;

function WlanOpenHandle(dwClientVersion: DWORD; pReserved: PVOID;
  out pdwNegotiatedVersion: DWORD; out phClientHandle: HANDLE): DWORD; stdcall;
  external wlanapi name 'WlanOpenHandle';

function WlanRegisterNotification(hClientHandle: HANDLE; dwNotifSource: DWORD;
  bIgnoreDuplicate: BOOL; funcCallback: TWLanNotificationCallback; pCallbackContext: PVOID;
  pReserved: PVOID; out pdwPrevNotifSource: DWORD): DWORD; stdcall;
  external wlanapi name 'WlanRegisterNotification';

并将它们称为：

// Define a callback procedure to handle the notifications
// You can supply a context pointer to any user information the callback
// may require (pointer to object, etc)
procedure OnWlanNotify(data : PWLanNotificationData; context : PVOID); stdcall;
begin
  // ShowMessage(IntToStr(data^.NotificationCode));  etc...
end;

// Register for notification
procedure TForm1.FormCreate(Sender: TObject);
var
  negotiatedVer : DWORD;
  prevSource : DWORD
begin
  if WlanOpenHandle(2, nil, negotiatedVer, FHandle) <> ERROR_SUCCESS then begin
    // handle error...
  end;
  // check negotiatedVersion if needed
  if WlanRegisterNotification(FHandle,
                       WLAN_NOTIFICATION_SOURCE_ACM,
                       LongBool(true),
                       @OnWlanNotify,
                       nil,
                       nil,
                       prevSource) <> ERROR_SUCCESS then begin
  end;

这会为您注册 WLAN 通知。您的回调函数将在收到通知后执行，通知的性质可以在传递给该方法的TWlanNotificationData 结构中找到。

您还应该在不再需要通知时取消注册。我在这里只实现了基本的错误检查。各种错误代码的详细信息可以在参考的 MSDN 文档中找到。

ACM 通知的（部分）列表：

const
  WLAN_NOTIFICATION_ACM_AUTOCONF_ENABLED = $00000001; 
    //Autoconfiguration is enabled.
  WLAN_NOTIFICATION_ACM_AUTOCONF_DISABLED = $00000002;
    //Autoconfiguration is disabled.
  WLAN_NOTIFICATION_ACM_BACKGROUND_SCAN_ENABLED = $00000003; 
    //Background scans are enabled.
  WLAN_NOTIFICATION_ACM_BACKGROUND_SCAN_DISABLED = $00000004;
    //Background scans are disabled.
  WLAN_NOTIFICATION_ACM_BSS_TYPE_CHANGE = $00000005;
    //The BSS type for an interface has changed.
  WLAN_NOTIFICATION_ACM_POWER_SETTING_CHANGE = $00000006;
    //The power setting for an interface has changed.
  WLAN_NOTIFICATION_ACM_SCAN_COMPLETE = $00000007;
    //A scan for networks has completed.
  WLAN_NOTIFICATION_ACM_SCAN_FAIL = $00000008;
    //A scan for connectable networks failed.
  WLAN_NOTIFICATION_ACM_CONNECTION_START = $00000009;
    //A connection has started to a network in range.
  WLAN_NOTIFICATION_ACM_CONNECTION_COMPLETE = $0000000a;
    //A connection has completed.
  WLAN_NOTIFICATION_ACM_CONNECTION_ATTEMPT_FAIL = $0000000b;
    //A connection attempt has failed.
  WLAN_NOTIFICATION_ACM_FILTER_LIST_CHANGE = $0000000c;
    //A change in the filter list has occurred, either through group policy or a call to the WlanSetFilterList function.
  WLAN_NOTIFICATION_ACM_INTERFACE_ARRIVAL = $0000000d;
    //A wireless LAN interface is been added to or enabled on the local computer.
  WLAN_NOTIFICATION_ACM_INTERFACE_REMOVAL = $0000000e;
    //A wireless LAN interface has been removed or disabled on the local computer.
  WLAN_NOTIFICATION_ACM_PROFILE_CHANGE = $0000000f;
    //A change in a profile or the profile list has occurred, either through group policy or by calls to Native Wifi functions.
  WLAN_NOTIFICATION_ACM_PROFILE_NAME_CHANGE = $00000010;
    //A profile name has changed, either through group policy or by calls to Native Wifi functions.
  WLAN_NOTIFICATION_ACM_PROFILES_EXHAUSTED = $00000011;
    //All profiles were exhausted in an attempt to autoconnect.
  WLAN_NOTIFICATION_ACM_NETWORK_NOT_AVAILABLE = $00000012;
    //The wireless service cannot find any connectable network after a scan.
  WLAN_NOTIFICATION_ACM_NETWORK_AVAILABLE = $00000013;
    //The wireless service found a connectable network after a scan, the interface was in the disconnected state, and there is no compatible auto-connect profile that the wireless service can use to connect .
  WLAN_NOTIFICATION_ACM_DISCONNECTING = $00000014;
    //The wireless service is disconnecting from a connectable network.
  WLAN_NOTIFICATION_ACM_DISCONNECTED = $00000015;
    //The wireless service has disconnected from a connectable network.
  WLAN_NOTIFICATION_ACM_ADHOC_NETWORK_STATE_CHANGE = $00000016;
    //A state change has occurred for an adhoc network.

第二个更详细的回调示例：

procedure OnWlanNotify(data : PWLanNotificationData; context : PVOID); stdcall;
begin
  case data^.NotificationCode of
    WLAN_NOTIFICATION_ACM_AUTOCONF_ENABLED : 
      TForm1(context^).Memo1.Lines.Add('Autoconfiguration is enabled.');
    WLAN_NOTIFICATION_ACM_AUTOCONF_DISABLED : 
      TForm1(context^).Memo1.Lines.Add('Autoconfiguration is disabled.');
    WLAN_NOTIFICATION_ACM_BACKGROUND_SCAN_ENABLED : 
      TForm1(context^).Memo1.Lines.Add('Background scans are enabled.');
    WLAN_NOTIFICATION_ACM_BACKGROUND_SCAN_DISABLED : 
      TForm1(context^).Memo1.Lines.Add('Background scans are disabled.');
    WLAN_NOTIFICATION_ACM_BSS_TYPE_CHANGE : 
      TForm1(context^).Memo1.Lines.Add('The BSS type for an interface has changed.');
    WLAN_NOTIFICATION_ACM_POWER_SETTING_CHANGE : 
      TForm1(context^).Memo1.Lines.Add('The power setting for an interface has changed.');
    WLAN_NOTIFICATION_ACM_SCAN_COMPLETE : 
      TForm1(context^).Memo1.Lines.Add('A scan for networks has completed.');
    WLAN_NOTIFICATION_ACM_SCAN_FAIL : 
      TForm1(context^).Memo1.Lines.Add('A scan for connectable networks failed.');
    WLAN_NOTIFICATION_ACM_CONNECTION_START : 
      TForm1(context^).Memo1.Lines.Add('A connection has started to a network in range.');
    WLAN_NOTIFICATION_ACM_CONNECTION_COMPLETE : 
      TForm1(context^).Memo1.Lines.Add('A connection has completed.');
    WLAN_NOTIFICATION_ACM_CONNECTION_ATTEMPT_FAIL : 
      TForm1(context^).Memo1.Lines.Add('A connection attempt has failed.');
    WLAN_NOTIFICATION_ACM_FILTER_LIST_CHANGE : 
      TForm1(context^).Memo1.Lines.Add('A change in the filter list has occurred, either through group policy or a call to the WlanSetFilterList function.');
    WLAN_NOTIFICATION_ACM_INTERFACE_ARRIVAL : 
      TForm1(context^).Memo1.Lines.Add('A wireless LAN interface is been added to or enabled on the local computer.');
    WLAN_NOTIFICATION_ACM_INTERFACE_REMOVAL : 
      TForm1(context^).Memo1.Lines.Add('A wireless LAN interface has been removed or disabled on the local computer.');
    WLAN_NOTIFICATION_ACM_PROFILE_CHANGE : 
      TForm1(context^).Memo1.Lines.Add('A change in a profile or the profile list has occurred, either through group policy or by calls to Native Wifi functions.');
    WLAN_NOTIFICATION_ACM_PROFILE_NAME_CHANGE : 
      TForm1(context^).Memo1.Lines.Add('A profile name has changed, either through group policy or by calls to Native Wifi functions.');
    WLAN_NOTIFICATION_ACM_PROFILES_EXHAUSTED : 
      TForm1(context^).Memo1.Lines.Add('All profiles were exhausted in an attempt to autoconnect.');
    WLAN_NOTIFICATION_ACM_NETWORK_NOT_AVAILABLE : 
      TForm1(context^).Memo1.Lines.Add('The wireless service cannot find any connectable network after a scan.');
    WLAN_NOTIFICATION_ACM_NETWORK_AVAILABLE : 
      TForm1(context^).Memo1.Lines.Add('The wireless service found a connectable network after a scan, the interface was in the disconnected state, and there is no compatible auto-connect profile that the wireless service can use to connect.');
    WLAN_NOTIFICATION_ACM_DISCONNECTING : 
      TForm1(context^).Memo1.Lines.Add('The wireless service is disconnecting from a connectable network.');
    WLAN_NOTIFICATION_ACM_DISCONNECTED : 
      TForm1(context^).Memo1.Lines.Add('The wireless service has disconnected from a connectable network.');
    WLAN_NOTIFICATION_ACM_ADHOC_NETWORK_STATE_CHANGE : 
      TForm1(context^).Memo1.Lines.Add('A state change has occurred for an adhoc network.');
  end;
end;

在上面的示例中，指向Form1 的指针被传递到用户上下文参数中。这在回调中传回，允许您从方法内访问该数据。

  if WlanRegisterNotification(FHandle,
                           WLAN_NOTIFICATION_SOURCE_ACM,
                           LongBool(true),
                           @OnWlanNotify,
                           @Form1,  // Pass in form pointer
                           nil,
                           prevSource) <> ERROR_SUCCESS then begin
    // handle error
  end;