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有2种方法:
用Mscomm32控件向接MODEM的串口发送“AT”命令,有回应“OK”就表示MODEM已打开,否则表示关闭。检测正在工作可用Mscomm32的CDHolding属性来判断(可参考VB帮助)。拨号后若MODEM返回“BUSY",则表示忙音。在执行前,必须先设置好MODEM,并可查看一些关于MODEM的AT命令的资料!如何检测是否已连接到Internet?
声明:Public Declare Function RasEnumConnections Lib "RasApi32.dll" _
Alias "RasEnumConnectionsA" (lpRasCon As Any, _
lpcb As Long, lpcConnections As Long) As Long
Public Declare Function RasGetConnectStatus Lib "RasApi32.dll" _
Alias "RasGetConnectStatusA" (ByVal hRasCon As Long, _
lpStatus As Any) As Long
Public Const RAS95_MaxEntryName = 256
Public Const RAS95_MaxDeviceType = 16
Public Const RAS95_MaxDeviceName = 32
Public Type RASCONN95
dwSize As Long
hRasCon As Long
szEntryName(RAS95_MaxEntryName) As Byte
szDeviceType(RAS95_MaxDeviceType) As Byte
szDeviceName(RAS95_MaxDeviceName) As Byte
End Type
Public Type RASCONNSTATUS95
dwSize As Long
RasConnState As Long
dwError As Long
szDeviceType(RAS95_MaxDeviceType) As Byte
szDeviceName(RAS95_MaxDeviceName) As Byte
End Type程序:
Private Sub main()
If IsConnected = True Then
MsgBox "已连接到Internet!", vbInformation, "提示"
Else
MsgBox "未连接到Internet!", vbInformation, "提示"
End If
End Sub
Public Function IsConnected() As Boolean
Dim TRasCon(255) As RASCONN95
Dim lg As Long
Dim lpcon As Long
Dim RetVal As Long
Dim Tstatus As RASCONNSTATUS95
'
TRasCon(0).dwSize = 412
lg = 256 * TRasCon(0).dwSize
'
RetVal = RasEnumConnections(TRasCon(0), lg, lpcon)
If RetVal <> 0 Then
MsgBox "产生错误!", vbInformation, "提示"
Exit Function
End If
'
Tstatus.dwSize = 160
RetVal = RasGetConnectStatus(TRasCon(0).hRasCon, Tstatus)
If Tstatus.RasConnState = &H2000 Then
IsConnected = True
Else
IsConnected = False
End If
End Function