by Martin Anbu Selvan (18 Submissions)
Category: Windows API Call/Explanation
Compatability: VB 6.0
Difficulty: Unknown Difficulty
Originally Published: Thu 26th February 2004
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
Retrive host name by IP Address.
VBcoders
Set obj = new clsIPRESOLVE 'or name that you used
obj. 'here the methods will pop up for you to use.
Class Module Code starts here:
Code:Option Explicit
Private mbInitialized As Boolean
Const WSADescription_Len = 256
Const WSASYS_Status_Len = 128
Const AF_INET = 4&
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)
'checks if string is valid IP address
Private Function CheckIP(IPToCheck As String) As Boolean
Dim TempValues
Dim iLoop As Long
Dim TempByte As Byte
On Error GoTo CheckIPError
TempValues = Split(IPToCheck, ".")
If UBound(TempValues) < 3 Then
Exit Function
End If
For iLoop = LBound(TempValues) To UBound(TempValues)
TempByte = TempValues(iLoop)
Next iLoop
CheckIP = True
CheckIPError:
End Function
'converts IP address from string to sin_addr
Private Function MakeIP(strIP As String) As Long
Dim vTemp
Dim lngTemp As Long
Dim iLoop As Long
On Error GoTo MakeIPError
vTemp = Split(strIP, ".")
For iLoop = 0 To (UBound(vTemp) - 1)
lngTemp = lngTemp + (vTemp(iLoop) * (256 ^ iLoop))
Next iLoop
If vTemp(UBound(vTemp)) < 128 Then
lngTemp = lngTemp + (vTemp(UBound(vTemp)) * (256 ^ 3))
Else
lngTemp = lngTemp + ((vTemp(UBound(vTemp)) - 256) * (256 ^ 3))
End If
MakeIP = lngTemp
MakeIPError:
End Function
'resolves IP address to host name
Private Function AddrToName(strAddr As String) As String
Dim heEntry As HOSTENT
Dim strHost As String * 255
Dim strTemp As String
Dim lngRet As Long
Dim lngIP As Long
On Error GoTo AddrToNameError
If CheckIP(strAddr) Then
lngIP = MakeIP(strAddr)
lngRet = gethostbyaddr(lngIP, 4, AF_INET)
If lngRet = 0 Then
Exit Function
End If
RtlMoveMemory heEntry, lngRet, Len(heEntry)
RtlMoveMemory ByVal strHost, heEntry.hName, 255
strTemp = TrimNull(strHost)
AddrToName = strTemp
End If
AddrToNameError:
End Function
'resolves host name to IP address
Private Function NameToAddr(ByVal strHost As String)
Dim ip_list() As Byte
Dim heEntry As HOSTENT
Dim strIPAddr As String
Dim lp_HostEnt As Long
Dim lp_HostIP As Long
Dim iLoop As Integer
On Error GoTo NameToAddrError
lp_HostEnt = gethostbyname(strHost)
If lp_HostEnt = 0 Then
Exit Function
End If
RtlMoveMemory heEntry, lp_HostEnt, LenB(heEntry)
RtlMoveMemory lp_HostIP, heEntry.hAddrList, 4
ReDim ip_list(1 To heEntry.hLength)
RtlMoveMemory ip_list(1), lp_HostIP, heEntry.hLength
For iLoop = 1 To heEntry.hLength
strIPAddr = strIPAddr & ip_list(iLoop) & "."
Next
strIPAddr = Mid(strIPAddr, 1, Len(strIPAddr) - 1)
NameToAddr = strIPAddr
NameToAddrError:
End Function
Public Function AddressToName(strIP As String) As String
If mbInitialized Then
AddressToName = AddrToName(strIP)
End If
End Function
Public Function NameToAddress(strName As String) As String
If mbInitialized Then
NameToAddress = NameToAddr(strName)
End If
End Function
Private Function TrimNull(sTrim As String) As String
Dim iFind As Long
iFind = InStr(1, sTrim, Chr(0))
If iFind > 0 Then
TrimNull = Left(sTrim, iFind - 1)
Else
TrimNull = sTrim
End If
End Function
Private Sub Class_Initialize()
Dim wsa As WSADATA
mbInitialized = (WSAStartup(257, wsa) = 0)
End Sub
Private Sub Class_Terminate()
If mbInitialized Then
WSACleanup
End If
End Sub