DNS Lookup

[D0ll]

I am trying to find out how to do a dns lookup without using a custom control. Does anyone know how?

Try this, i found it somewhere couple of months ago.

Option Explicit

Const WSADescription_Len = 256
Const WSASYS_Status_Len = 128
Private Type HOSTENT
  hName As Long
  hAliases As Long
  hAddrType As Integer
  hLength As Integer
  hAddrList As Long
End Type
Private Type WSADATA
  wversion As Integer
  wHighVersion As Integer
  szDescription(0 To WSADescription_Len) As Byte
  szSystemStatus(0 To WSASYS_Status_Len) As Byte
  iMaxSockets As Integer
  iMaxUdpDg As Integer
  lpszVendorInfo As Long
End Type

Private Declare Function WSAStartup Lib "wsock32" (ByVal VersionReq As Long, WSADataReturn As WSADATA) As Long
Private Declare Function WSACleanup Lib "wsock32" () As Long
Private Declare Function WSAGetLastError Lib "wsock32" () As Long
Private Declare Function gethostbyaddr Lib "wsock32" (addr As Long, addrLen As Long, addrType As Long) As Long
Private Declare Function gethostbyname Lib "wsock32" (ByVal hostname As String) As Long
Private Declare Sub RtlMoveMemory Lib "kernel32" (hpvDest As Any, ByVal hpvSource As Long, ByVal cbCopy As Long)

Public Event Error(ByVal Number As Long, Description As String)
Public Event ResolveCompleted()

'checks if string is valid IP address
Private Function IsIP(ByVal strIP As String) As Boolean
    On Error Resume Next
    Dim t As String: Dim s As String: Dim i As Integer
    s = strIP
    While InStr(s, ".") <> 0
        t = Left(s, InStr(s, ".") - 1)
        If IsNumeric(t) And Val(t) >= 0 And Val(t) <= 255 Then
            s = Mid(s, InStr(s, ".") + 1)
        Else
            Exit Function
        End If
        i = i + 1
    Wend
    t = s
    If IsNumeric(t) And InStr(t, ".") = 0 And Len(t) = Len(Trim(Str(Val(t)))) And Val(t) >= 0 And Val(t) <= 255 And strIP <> "255.255.255.255" And i = 3 Then
        IsIP = True
    End If
    If Err.Number > 0 Then
        RaiseEvent Error(Err.Number, Err.Description)
        Err.Clear
    End If
End Function

'converts IP address from string to sin_addr
Private Function MakeIP(strIP As String) As Long
    On Error Resume Next
    Dim lIP As Long
    lIP = Left(strIP, InStr(strIP, ".") - 1)
    strIP = Mid(strIP, InStr(strIP, ".") + 1)
    lIP = lIP + Left(strIP, InStr(strIP, ".") - 1) * 256
    strIP = Mid(strIP, InStr(strIP, ".") + 1)
    lIP = lIP + Left(strIP, InStr(strIP, ".") - 1) * 256 * 256
    strIP = Mid(strIP, InStr(strIP, ".") + 1)
    If strIP < 128 Then
        lIP = lIP + strIP * 256 * 256 * 256
    Else
        lIP = lIP + (strIP - 256) * 256 * 256 * 256
    End If
    MakeIP = lIP
    If Err.Number > 0 Then
        RaiseEvent Error(Err.Number, Err.Description)
        Err.Clear
    End If
End Function

'resolves IP address to host name
Private Function NameByAddr(strAddr As String) As String
    On Error Resume Next
    Dim nRet As Long
    Dim lIP As Long
    Dim strHost As String * 255: Dim strTemp As String
    Dim hst As HOSTENT
    
    If IsIP(strAddr) Then
        lIP = MakeIP(strAddr)
        nRet = gethostbyaddr(lIP, 4, 2)
        If nRet <> 0 Then
            RtlMoveMemory hst, nRet, Len(hst)
            RtlMoveMemory ByVal strHost, hst.hName, 255
            strTemp = strHost
            If InStr(strTemp, Chr(10)) <> 0 Then
                strTemp = Left(strTemp, InStr(strTemp, Chr(0)) - 1)
            End If
            strTemp = Trim(strTemp)
            NameByAddr = strTemp
        Else
            RaiseEvent Error(9003, "Host name not found")
            Exit Function
        End If
    Else
        RaiseEvent Error(9002, "Invalid IP address")
        Exit Function
    End If
    If Err.Number > 0 Then
        RaiseEvent Error(Err.Number, Err.Description)
        Err.Clear
    End If
End Function

'resolves host name to IP address
Private Function AddrByName(ByVal strHost As String)
    On Error Resume Next
    Dim hostent_addr As Long
    Dim hst As HOSTENT
    Dim hostip_addr As Long
    Dim temp_ip_address() As Byte
    Dim i As Integer
    Dim ip_address As String
    If IsIP(strHost) Then
        AddrByName = strHost
        Exit Function
    End If
    hostent_addr = gethostbyname(strHost)
    If hostent_addr = 0 Then
        RaiseEvent Error(9001, "Can't resolve hst")
        Exit Function
    End If
    RtlMoveMemory hst, hostent_addr, LenB(hst)
    RtlMoveMemory hostip_addr, hst.hAddrList, 4
    ReDim temp_ip_address(1 To hst.hLength)
    RtlMoveMemory temp_ip_address(1), hostip_addr, hst.hLength
    For i = 1 To hst.hLength
        ip_address = ip_address & temp_ip_address(i) & "."
    Next
    ip_address = Mid(ip_address, 1, Len(ip_address) - 1)
    AddrByName = ip_address
    If Err.Number > 0 Then
        RaiseEvent Error(Err.Number, Err.Description)
        Err.Clear
    End If
End Function

Public Function AddressToName(strIP As String)
    AddressToName = NameByAddr(strIP)
    RaiseEvent ResolveCompleted
End Function

Public Function NameToAddress(strName As String)
    NameToAddress = AddrByName(strName)
    RaiseEvent ResolveCompleted
End Function

Private Sub Class_Initialize()
    Dim udtWSAData As WSADATA
    If WSAStartup(257, udtWSAData) Then RaiseEvent Error(Err.LastDllError, Err.Description)
End Sub

Private Sub Class_Terminate()
    WSACleanup
End Sub

------------------

Vincent van den Braken
EMail: azzmodan@azzmodan.demon.nl
ICQ: 15440110
Homepage: http://www.azzmodan.demon.nl





[This message has been edited by Azzmodan (edited 11-09-1999).]