如果是检查winsock的连接状态可以用，if winsock1.state=*
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sckClosed 0 缺省的。关闭
sckOpen 1 打开
sckListening 2 侦听
sckConnectionPending 3 连接挂起
sckResolvingHost 4 识别主机
sckHostResolved 5 已识别主机
sckConnecting 6 正在连接
sckConnected 7 已连接
sckClosing 8 同级人员正在关闭连接
sckError 9 错误
*值得就是上述值的一个，然后在后面添加代码！例如要判断时候关闭，就可以
if winsock1.state=0 then msgbox "未连接!"
这样的没有连接就会弹出对话框了
首先添加一模块，代码如下
Option Explicit
Private Const IP_SUCCESS As Long = 0
Private Const IP_STATUS_BASE As Long = 11000
Private Const IP_BUF_TOO_SMALL As Long = (11000 + 1)
Private Const IP_DEST_NET_UNREACHABLE As Long = (11000 + 2)
Private Const IP_DEST_HOST_UNREACHABLE As Long = (11000 + 3)
Private Const IP_DEST_PROT_UNREACHABLE As Long = (11000 + 4)
Private Const IP_DEST_PORT_UNREACHABLE As Long = (11000 + 5)
Private Const IP_NO_RESOURCES As Long = (11000 + 6)
Private Const IP_BAD_OPTION As Long = (11000 + 7)
Private Const IP_HW_ERROR As Long = (11000 + 8)
Private Const IP_PACKET_TOO_BIG As Long = (11000 + 9)
Private Const IP_REQ_TIMED_OUT As Long = (11000 + 10)
Private Const IP_BAD_REQ As Long = (11000 + 11)
Private Const IP_BAD_ROUTE As Long = (11000 + 12)
Private Const IP_TTL_EXPIRED_TRANSIT As Long = (11000 + 13)
Private Const IP_TTL_EXPIRED_REASSEM As Long = (11000 + 14)
Private Const IP_PARAM_PROBLEM As Long = (11000 + 15)
Private Const IP_SOURCE_QUENCH As Long = (11000 + 16)
Private Const IP_OPTION_TOO_BIG As Long = (11000 + 17)
Private Const IP_BAD_DESTINATION As Long = (11000 + 18)
Private Const IP_ADDR_DELETED As Long = (11000 + 19)
Private Const IP_SPEC_MTU_CHANGE As Long = (11000 + 20)
Private Const IP_MTU_CHANGE As Long = (11000 + 21)
Private Const IP_UNLOAD As Long = (11000 + 22)
Private Const IP_ADDR_ADDED As Long = (11000 + 23)
Private Const IP_GENERAL_FAILURE As Long = (11000 + 50)
Private Const MAX_IP_STATUS As Long = (11000 + 50)
Private Const IP_PENDING As Long = (11000 + 255)
Private Const PING_TIMEOUT As Long = 500
Private Const WS_VERSION_REQD As Long = H101
Private Const MIN_SOCKETS_REQD As Long = 1
Private Const SOCKET_ERROR As Long = -1
Private Const INADDR_NONE As Long = HFFFFFFFF
Private Const MAX_WSADescription As Long = 256
Private Const MAX_WSASYSStatus As Long = 128
Public PingTime As Long
Private Type ICMP_OPTIONS
Ttl As Byte
Tos As Byte
Flags As Byte
OptionsSize As Byte
OptionsData As Long
End Type
Private Type ICMP_ECHO_REPLY
Address As Long
status As Long
RoundTripTime As Long
DataSize As Long
DataPointer As Long
Options As ICMP_OPTIONS
Data As String * 250
End Type
Private Type WSADATA
wVersion As Integer
wHighVersion As Integer
szDescription(0 To MAX_WSADescription) As Byte
szSystemStatus(0 To MAX_WSASYSStatus) As Byte
wMaxSockets As Long
wMaxUDPDG As Long
dwVendorInfo As Long
End Type
Public Declare Function timeGetTime Lib "winmm.dll" () As Long
Private Declare Function WSAStartup Lib "wsock32" (ByVal wVersionRequired As Long, lpWSADATA As WSADATA) As Long
Private Declare Function WSACleanup Lib "wsock32" () As Long
Private Declare Function IcmpCreateFile Lib "icmp.dll" () As Long
Private Declare Function inet_addr Lib "wsock32" (ByVal s As String) As Long
Private Declare Function IcmpCloseHandle Lib "icmp.dll" (ByVal IcmpHandle As Long) As Long
Private Declare Function IcmpSendEcho Lib "icmp.dll" (ByVal IcmpHandle As Long, ByVal DestinationAddress As Long, ByVal RequestData As String, ByVal RequestSize As Long, ByVal RequestOptions As Long, ReplyBuffer As ICMP_ECHO_REPLY, ByVal ReplySize As Long, ByVal Timeout As Long) As Long
'Private Declare Function WSAGetLastError Lib "wsock32" () As Long
'Private Declare Function gethostname Lib "wsock32" (ByVal szHost As String, ByVal dwHostLen As Long) As Long
'Private Declare Function gethostbyname Lib "wsock32" (ByVal szHost As String) As Long
'Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (xDest As Any, xSource As Any, ByVal nbytes As Long)
Private Function GetStatusCode(status As Long) As String
On Error GoTo ErrLine
Dim Msg As String
GetStatusCode = ""
Select Case status
Case IP_SUCCESS: Msg = "ip success"
Case INADDR_NONE: Msg = "inet_addr: bad IP format"
Case IP_BUF_TOO_SMALL: Msg = "ip buf too_small"
Case IP_DEST_NET_UNREACHABLE: Msg = "ip dest net unreachable"
Case IP_DEST_HOST_UNREACHABLE: Msg = "ip dest host unreachable"
Case IP_DEST_PROT_UNREACHABLE: Msg = "ip dest port unreachable"
Case IP_DEST_PORT_UNREACHABLE: Msg = "ip dest port unreachable"
Case IP_NO_RESOURCES: Msg = "ip no resources"
Case IP_BAD_OPTION: Msg = "ip bad option"
Case IP_HW_ERROR: Msg = "ip hw_error"
Case IP_PACKET_TOO_BIG: Msg = "ip packet too_big"
Case IP_REQ_TIMED_OUT: Msg = "ip req timed out"
Case IP_BAD_REQ: Msg = "ip bad req"
Case IP_BAD_ROUTE: Msg = "ip bad route"
Case IP_TTL_EXPIRED_TRANSIT: Msg = "ip ttl expired transit"
Case IP_TTL_EXPIRED_REASSEM: Msg = "ip ttl expired reassem"
Case IP_PARAM_PROBLEM: Msg = "ip param_problem"
Case IP_SOURCE_QUENCH: Msg = "ip source quench"
Case IP_OPTION_TOO_BIG: Msg = "ip option too_big"
Case IP_BAD_DESTINATION: Msg = "ip bad destination"
Case IP_ADDR_DELETED: Msg = "ip addr deleted"
Case IP_SPEC_MTU_CHANGE: Msg = "ip spec mtu change"
Case IP_MTU_CHANGE: Msg = "ip mtu_change"
Case IP_UNLOAD: Msg = "ip unload"
Case IP_ADDR_ADDED: Msg = "ip addr added"
Case IP_GENERAL_FAILURE: Msg = "ip general failure"
Case IP_PENDING: Msg = "ip pending"
Case PING_TIMEOUT: Msg = "ping timeout"
Case Else: Msg = "unknown msg returned"
End Select
GetStatusCode = Msg
Exit Function
ErrLine:
End Function
Private Function Ping(sAddress As String, sDataToSend As String, ECHO As ICMP_ECHO_REPLY) As Long
On Error GoTo ErrLine
Dim hPort As Long
Dim dwAddress As Long
dwAddress = inet_addr(sAddress)
If dwAddress INADDR_NONE Then
hPort = IcmpCreateFile()
If hPort Then
Call IcmpSendEcho(hPort, dwAddress, sDataToSend, Len(sDataToSend), 0, ECHO, Len(ECHO), PING_TIMEOUT)
Ping = ECHO.status
Call IcmpCloseHandle(hPort)
End If
Else
Ping = INADDR_NONE
End If
Exit Function
ErrLine:
Ping = INADDR_NONE
End Function
Public Function PingIP(ByVal szIp As String) As Boolean
On Error GoTo ErrLine
Dim WSAD As WSADATA
Dim ECHO As ICMP_ECHO_REPLY
Dim ret As Long
'Delay 150
PingIP = False
PingTime = Empty
If WSAStartup(WS_VERSION_REQD, WSAD) = IP_SUCCESS Then
ret = Ping(Trim(szIp), "tanaya", ECHO)
PingTime = ECHO.RoundTripTime
If InStr(1, GetStatusCode(ret), "success") 0 Then
WSACleanup
PingIP = True
PingTime = ECHO.RoundTripTime
Exit Function
End If
End If
Exit Function
ErrLine:
End Function
然后建立一窗体，一command
Private Sub Command1_Click()
If PingIP("你需要访问的ip") = True Then
'你自己增加需要执行的代码
else
'增加不联网时需要执行的代码
end if
Private Declare Function PathFileExists Lib "shlwapi.dll" Alias "PathFileExistsA" (ByVal pszPath As String) As Long
这是封装在Shell32.DLL系统文件里的一个函数，既可以判断本地文件是否存在，又可以判断远程电脑上的文件是否存在。函数返回值是个Long型变量，返回两个值0,1。1表示文件存在(True),0表示文件不存在(False)。而且只有一个参数szPath,是个字符串变量，如果要判断本地的文件是否存在其路径可写为：”C:\Windows\Config\SysBook.Txt”)，如果文件在远程电脑上，其路径可写为（假设对方电脑IP为192.168.0.2)
"\\192.168.0.2\d$\javatools\somefile.txt",如果其电脑名为WorkStation可写为
“\\workstation\javatools\somefile.txt"，当然这个函数还可以查找网站上的网页文件如：""
我们可以写个简单的自定义公用函数来完成这个功能，在自定义函数里调用这个API函数
Public Function GetFileExists(ByVal FileName As String) As Boolean
If FileName = "" Then
MsgBox "请输入文件名", vbInformation, "提示"
Exit Function
Else
GetFileExists = CBool(PathFileExists(FileName))
End If
End Function
在窗体界面上加一按钮,和一文本框
Private Sub Command1_Click()
Dim T As Boolean
T = GetFileExists("F:\it\Develope\Retail\Bill\vssver.scc")
If T = True Then
Text1.Text = "该文件存在"
Else
Text1.Text = "该文件不存在"
End If
End Sub
当然GetFileExists其中的参数还可以写成
"\\192.168.0.2\d$\javatools\somefile.txt"
"\\workstation\javatools\somefile.txt"
""
这个函数除了能判断文件是否存在外，还可以判断本地或远程文件夹
是否存在，我觉得这要比用Dir这个VB自带函数来判断文件是否存在要好用多了，而且也不需要调用FileSystemObject组件来操作了。
serverstring = "Server=" 服务器IP ";DataBase=" 库名 ";Userid=" 用户名 ";Password=" 密码
Try
Conn = New MySqlConnection(serverstring)
Conn.Open()
MsgBox("连接成功")
Conn.Dispose()
Conn.Close()
Catch ex As Exception
MsgBox("连接失败！")
End Try
这是 mysql 的，自己改成 sql server 的就行了
Microsoft.VisualBasic.Devices.Network.IsAvailable As Boolean
生成实例后可以通过此属性来获取是否联网的值，True代表已联网，False代表没有联网
Microsoft.VisualBasic.Devices.Network.NetworkAvailabilityChanged(ByVal Object, ByVal Microsoft.VisualBasic.Devices.NetworkAvailableEventArgs)
该事件是在电脑断开/连上互联网是引发的
其中：
e.IsNetworkAvailable
的功能同Microsoft.VisualBasic.Devices.Network.IsAvailable
实例:
Dim netListener As New Microsoft.VisualBasic.Devices.Network '生成实例
If netListener.IsAvailable = True Then
MsgBox("已联网")
Else
MsgBox("未联网")
End If
NetworkAvailabilityChanged实例：
WithEvents netListener As New Microsoft.VisualBasic.Devices.Network '生成实例
Private Sub OnNetworkChanged(ByVal Object, ByVal Microsoft.VisualBasic.Devices.NetworkAvailableEventArgs)Handles netListener.NetworkAvailabilityChanged
If e.IsNetworkAvailable = True Then
MsgBox("已联网")
Else
MsgBox("未联网")
End If
End Sub
你这段代码可以获得该主机名下的所有ip，每个ip地址都是有类型簇的，可以区别本地地址和网络地址、ip6地址。
你获取索引为0的ip，不一定是正确的网络地址，它有时顺序在中间，在后面。
应该获取所有ip，再通过ip地址簇类型区分
判断连接本身有一个函数，不过有时没联网也是真。
可以用ping，ping百度、ping访问速度快、不经常维护断线的网络主机。
