判斷網絡是否已經斷線

'API函數定義
Dim eR As EIGCInte.netConnectionState
Dim sMsg As String
Dim sName As String
Dim bConnected As Boolean

Private Declare Function InternetSetDialState Lib "wininet.dll" _
(ByVal lpszConnectoid As String, ByVal dwState As Long, _
ByVal dwReserved As Long) As Long

Private Declare Function InternetOpen Lib "wininet.dll" Alias "InternetOpenA" _
(ByVal sAgent As String, ByVal lAclearcase/" target="_blank" >ccessType As Long, ByVal sProxyName As String, _
ByVal sProxyBypass As String, ByVal lFlags As Long) As Long

Private Declare Function InternetGetConnectedStateEx Lib "wininet.dll" _
Alias "InternetGetConnectedStateExA" _
(ByRef lpdwFlags As Long, _
ByVal lpszConnectionName As String, _
ByVal dwNameLen As Long, _
ByVal dwReserved As Long _
) As Long
Private Enum EIGCInternetConnectionState
INTERNET_CONNECTION_MODEM = &H1&
INTERNET_CONNECTION_LAN = &H2&
INTERNET_CONNECTION_PROXY = &H4&
INTERNET_RAS_INSTALLED = &H10&
INTERNET_CONNECTION_OFFLINE = &H20&
INTERNET_CONNECTION_CONFIGURED = &H40&
End Enum

'InternetConnected 函數判斷是否連接到Internet的函數
'獲得是否以及通過何中方式連接到Internet上
Private Function InternetConnected(Optional ByRef eConnectionInfo _
As EIGCInternetConnectionState, Optional ByRef _
sConnectionName As String) As Boolean

Dim dwFlags As Long
Dim sNameBuf As String
Dim lR As Long
Dim iPos As Long

sNameBuf = String$(513, 0)
lR = InternetGetConnectedStateEx(dwFlags, sNameBuf, 512, 0&)
eConnectionInfo = dwFlags
iPos = InStr(sNameBuf, vbNullChar)
If iPos > 0 Then
sConnectionName = Left$(sNameBuf, iPos - 1)
ElseIf Not sNameBuf = String$(513, 0) Then
sConnectionName = sNameBuf
End If
InternetConnected = (lR = 1)
End Function

'InternetConnected 函數的調用

'檢測是否已經以及使用什么方法連接到Internet
bConnected = InternetConnected(eR, sName)


'根據獲得的結果輸出
If (eR And INTERNET_CONNECTION_MODEM) = INTERNET_CONNECTION_MODEM Then
sMsg = sMsg & "使用modem連接到Internet." & vbCrLf
End If
If (eR And INTERNET_CONNECTION_LAN) = INTERNET_CONNECTION_LAN Then
sMsg = sMsg & "使用內部網連接到Internet." & vbCrLf
End If
If (eR And INTERNET_CONNECTION_PROXY) = INTERNET_CONNECTION_PROXY Then
sMsg = sMsg & "通過代理服務器連接到Internet." & vbCrLf
End If
If (eR And INTERNET_CONNECTION_OFFLINE) = INTERNET_CONNECTION_OFFLINE Then
sMsg = sMsg & "現在連接處于離線狀態." & vbCrLf
End If
If (eR And INTERNET_CONNECTION_CONFIGURED) = INTERNET_CONNECTION_CONFIGURED Then
sMsg = sMsg & "連接已經被設定." & vbCrLf
Else
sMsg = sMsg & "沒有設定好的連接." & vbCrLf
End If
If (eR And INTERNET_RAS_INSTALLED) = INTERNET_RAS_INSTALLED Then
sMsg = sMsg & "本機已經安裝了遠程訪問服務功能." & vbCrLf
End If

'顯示連接名稱
If bConnected Then
sMsg = "已連接到Internet,連接名稱: " & sName & vbCrLf & vbCrLf & sMsg
Else
sMsg = "沒有連接到Internet,連接名稱: " & sName & vbCrLf & vbCrLf & sMsg
End If

原文轉自：http://www.anti-gravitydesign.com