我做了一个服务端程序和客户端程序,我每次启动客户端需要判断服务端是否在网上,然后在相应的做出反应,现在我不知道怎么判断服务器是否在网上,在程序外面我可以通过ping 命令来判断,不知道在vb中我怎么判断?望高手赐教!
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详细请参考SOCKET和INTERNET API
也可去http://www.allapi.net/,上面有详细的介绍
你可以通过on error goto err来知道服务器是否在网上
API函数进行PING操作?怎么操作?说的详细点行吗?
应该是调用wininet.dll的。
你去上面我说的那个网站找找看,而且网上也有很多这样的实例。
我现在手头无任何编程环境,只能这样帮你了。
Const SOCKET_ERROR = 0
Private Type WSAdata
wVersion As Integer
wHighVersion As Integer
szDescription(0 To 255) As Byte
szSystemStatus(0 To 128) As Byte
iMaxSockets As Integer
iMaxUdpDg As Integer
lpVendorInfo As Long
End Type
Private Type Hostent
h_name As Long
h_aliases As Long
h_addrtype As Integer
h_length As Integer
h_addr_list As Long
End Type
Private Type IP_OPTION_INFORMATION
TTL As Byte
Tos As Byte
Flags As Byte
OptionsSize As Long
OptionsData As String * 128
End Type
Private Type IP_ECHO_REPLY
Address(0 To 3) As Byte
Status As Long
RoundTripTime As Long
DataSize As Integer
Reserved As Integer
data As Long
Options As IP_OPTION_INFORMATION
End Type
Private Declare Function GetHostByName Lib "wsock32.dll" Alias "gethostbyname" (ByVal HostName As String) As Long
Private Declare Function WSAStartup Lib "wsock32.dll" (ByVal wVersionRequired&, lpWSAdata As WSAdata) As Long
Private Declare Function WSACleanup Lib "wsock32.dll" () As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (hpvDest As Any, hpvSource As Any, ByVal cbCopy As Long)
Private Declare Function IcmpCreateFile Lib "icmp.dll" () As Long
Private Declare Function IcmpCloseHandle Lib "icmp.dll" (ByVal HANDLE As Long) As Boolean
Private Declare Function IcmpSendEcho Lib "ICMP" (ByVal IcmpHandle As Long, ByVal DestAddress As Long, ByVal RequestData As String, ByVal RequestSize As Integer, RequestOptns As IP_OPTION_INFORMATION, ReplyBuffer As IP_ECHO_REPLY, ByVal ReplySize As Long, ByVal TimeOut As Long) As Boolean
Private Sub Form_Load()
'KPD-Team 2000
'URL: http://www.allapi.net/
'E-Mail: [email protected]
Const HostName = "www.allapi.net"
Dim hFile As Long, lpWSAdata As WSAdata
Dim hHostent As Hostent, AddrList As Long
Dim Address As Long, rIP As String
Dim OptInfo As IP_OPTION_INFORMATION
Dim EchoReply As IP_ECHO_REPLY
Call WSAStartup(&H101, lpWSAdata)
If GetHostByName(HostName + String(64 - Len(HostName), 0)) <> SOCKET_ERROR Then
CopyMemory hHostent.h_name, ByVal GetHostByName(HostName + String(64 - Len(HostName), 0)), Len(hHostent)
CopyMemory AddrList, ByVal hHostent.h_addr_list, 4
CopyMemory Address, ByVal AddrList, 4
End If
hFile = IcmpCreateFile()
If hFile = 0 Then
MsgBox "Unable to Create File Handle"
Exit Sub
End If
OptInfo.TTL = 255
If IcmpSendEcho(hFile, Address, String(32, "A"), 32, OptInfo, EchoReply, Len(EchoReply) + 8, 2000) Then
rIP = CStr(EchoReply.Address(0)) + "." + CStr(EchoReply.Address(1)) + "." + CStr(EchoReply.Address(2)) + "." + CStr(EchoReply.Address(3))
Else
MsgBox "Timeout"
End If
If EchoReply.Status = 0 Then
MsgBox "Reply from " + HostName + " (" + rIP + ") recieved after " + Trim$(CStr(EchoReply.RoundTripTime)) + "ms"
Else
MsgBox "Failure ..."
End If
Call IcmpCloseHandle(hFile)
Call WSACleanup
End Sub