VB 利用gethostbyname判断网络是否连接
GetHostbyName API可获取域名对应的IP地址,当没有联网状态将会返回一个错误值。所以可利用它来判断是否联网。
Private Sub Form_Load()
If IsConnectedState Then
MsgBox "连接网络"
Else
MsgBox "没有联网"
End If
End Sub
Option Explicit
Private Type WSADATA
wversion As Integer
wHighVersion As Integer
szDescription(0 To 256) As Byte
szSystemStatus(0 To 128) As Byte
iMaxSockets As Integer
iMaxUdpDg As Integer
lpszVendorInfo As Long
End Type
Private Declare Function WSAStartup Lib "WSOCK32.DLL" (ByVal wVersionRequired As Integer, lpWSAData As WSADATA) As Long
Private Declare Function WSACleanup Lib "WSOCK32.DLL" () As Long
Private Declare Function gethostbyname Lib "WSOCK32.DLL" (ByVal szHostname As String) As Long
Private Const WS_VERSION_REQD = &H101
Public Function IsConnectedState() As Boolean
Dim udtWSAD As WSADATA
Call WSAStartup(WS_VERSION_REQD, udtWSAD)
IsConnectedState = CBool(gethostbyname("www.baidu.com"))
Call WSACleanup
End Function
------------------------------------------------------
如果程序在联网处理之前能先自动判断用户是否已经联网，就可提高程序运行效率。
Private Sub Form_Load()
If IsConnected = TRUE Then
MsgBox (“您已经连通了Internet!”)
End If
If IsConnected = FALSE Then
MsgBox (“您还没有连通 Internet!”)
End If
End Sub
Option Explicit
/＊有关的API声明和定义＊/
Public Declare Function RasEnumConnections Lib “RasApi32.dll” Alias “RasEnumConnectionsA” (lpRasCon As Any, lpcb As Long, lpcConnections As Long) As Long
#p#分页标题#e#
Public Declare Function RasGetConnectStatus Lib “RasApi32.dll” Alias “RasGetConnectStatusA” (ByVal hRasCon As Long, lpStatus As Any) As Long
/＊常数和变量的设定＊/
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
/＊函数IsConnected返回连通的状态，如果为True则表示已连通＊/
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 “错误”
#p#分页标题#e#
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
----------------------------------------------------
这个函数判断挺好,但在网络不通时连接比较慢
API 函数声明
Public Declare Function InternetCheckConnection Lib "wininet.dll" Alias "InternetCheckConnectionA" (ByVal lpszUrl As String, ByVal dwflags As Long, ByVal dwReserved As Long) As Long
Private Sub Form_Load()
If InternetCheckConnection("http://www.baidu.com/", 1, 0) = 0 Then
MsgBox "网络不正常"
Else
MsgBox "网络正常"
End If
End Sub
---------------------------------------
这个函数比较快,但有时判断不准确
Private Type WSADATA
wversion As Integer
wHighVersion As Integer
szDescription(0 To 256) As Byte
szSystemStatus(0 To 128) As Byte
iMaxSockets As Integer
iMaxUdpDg As Integer
lpszVendorInfo As Long
End Type
#p#分页标题#e#Private Declare Function WSAStartup Lib "WSOCK32.DLL" (ByVal wVersionRequired As Integer, lpWSAData As WSADATA) As Long
Private Declare Function WSACleanup Lib "WSOCK32.DLL" () As Long
Private Declare Function gethostbyname Lib "WSOCK32.DLL" (ByVal szHostname As String) As Long
Private Const WS_VERSION_REQD = &H101
Public Function IsConnectedState() As Boolean
Dim udtWSAD As WSADATA
Call WSAStartup(WS_VERSION_REQD, udtWSAD)
IsConnectedState = CBool(gethostbyname("www.baidu.com"))
Call WSACleanup
End Function
