vb@rchiv · Extra-Tipps · Hostname in IP-Adresse umwandeln und umgekehrt

Rubrik: | VB-Versionen: VB4, VB5, VB6

01.11.03

Hostname in IP-Adresse umwandeln und umgekehrt Dieser Tipp zeigt, wie man den Rechner-/Servername anhand einer IP-Adresse ermittelt und umgekehrt.
Autor: Dieter Otter	Bewertung:	Views: 1.814
http://www.tools4vb.de/	System: Win9x, WinNT, Win2k, WinXP, Win7, Win8, Win10, Win11	Beispielprojekt

Oftmals kennt man eine IP-Adresse eines Rechners im lokalen LAN oder auch im Internet (Webserver), aber leider nicht den Hostnamen (Rechnername). Oder umgekehrt: Man kennt den Hostnamen und möchte anhand des Namens die IP-Adresse des Rechners/Servers ermitteln.

Wie das geht, das zeigt wir Ihnen heute. Das Windows-API und in diesem Fall speziell die WSOCK32.DLL stellt uns hierfür folgende Funktionen bereit, die wir nur noch entsprechend nutzen müssen

gethostbyname: Ermitteln der IP-Adresse anhand eines Hostnamen
gethostbyaddr: Ermitteln des Hostnamen anhand einer IP-Adresse

Fügen Sie nachfolgenden Code in ein Modul:

Option Explicit
 
' Benötigte API-Deklarationen
Private Const WS_VERSION_REQD As Long = &H101
Private Const MAX_WSADescription = 256
Private Const MAX_WSASYSStatus = 128
Private Const ERROR_SUCCESS = 0&
 
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 Integer
  wMaxUDPDG As Integer
  dwVendorInfo As Long
End Type
 
Private Type HOSTENT
  hName As Long
  hAliases As Long
  hAddrType As Integer
  hLen As Integer
  hAddrList As Long
End Type
 
Private Declare Function WSAStartup Lib "WSOCK32.DLL" ( _
  ByVal wVersionRequired As Long, _
  lpWSADATA As WSAData) As Long
 
Private Declare Function WSACleanup Lib "WSOCK32.DLL" () As Long
 
Private Declare Function gethostbyname Lib "WSOCK32.DLL" ( _
  ByVal szHost As String) As Long
 
Private Declare Function gethostbyaddr Lib "WSOCK32.DLL" ( _
  lpIP As Long, _
  ByVal nLength As Integer, _
  ByVal nType As Long) As Long
 
Private Declare Function inet_addr Lib "WSOCK32.DLL" ( _
  ByVal szIP As String) As Long
 
Private Declare Sub CopyMemory Lib "kernel32" _
  Alias "RtlMoveMemory" ( _
  lpDest As Any, _
  ByVal lpSource As Long, _
  ByVal cbCopy As Long)

' Ermittelt den Rechner-/Servername (Hostname)
' anhand einer IP-Adresse
Public Function GetHostFromIP(ByVal sIPAddress As String) As String
  Dim WSAD As WSAData
  Dim nIP As Long
  Dim nResult As Long
  Dim nLen As Long
  Dim sHostname As String
  Dim m_Host As HOSTENT
 
  If WSAStartup(WS_VERSION_REQD, WSAD) = ERROR_SUCCESS Then
    nIP = inet_addr(sIPAddress)
    nResult = gethostbyaddr(nIP, 4, 2)
    If nResult <> 0 Then
      nLen = Len(m_Host)
      sHostname = String$(260, 0)
      CopyMemory m_Host, nResult, nLen
      CopyMemory ByVal sHostname, m_Host.hName, 260
      sHostname = Left$(sHostname, InStr(sHostname, Chr$(0)) - 1)
    End If
    Call WSACleanup
  End If
  GetHostFromIP = sHostname
End Function

' Ermittelt die IP-Adresse anhand eines
' Rechner-/Server-Namens (Hostname)
Public Function GetIPFromHost(ByVal sHostname As String) As String
  Dim WSAD As WSAData
  Dim nHost As Long
  Dim nIP As Long
  Dim nTemp() As Byte
  Dim m_Host As HOSTENT
  Dim sIPAddress As String
  Dim i As Long
 
  If WSAStartup(WS_VERSION_REQD, WSAD) = ERROR_SUCCESS Then
    nHost = gethostbyname(ByVal Replace(sHostname, "\", ""))
    If nHost <> 0 Then
      CopyMemory m_Host, ByVal nHost, ByVal Len(m_Host)
      CopyMemory nIP, ByVal m_Host.hAddrList, ByVal 4
      ReDim nTemp(1 To m_Host.hLen)
      CopyMemory nTemp(1), ByVal nIP, ByVal m_Host.hLen
 
      For i = 1 To m_Host.hLen
        sIPAddress = sIPAddress & nTemp(i) & "."
      Next i
      sIPAddress = Left$(sIPAddress, Len(sIPAddress) - 1)
    End If
    Call WSACleanup
  End If
 
  GetIPFromHost = sIPAddress
End Function

Aufruf:

' IP anhand eines Rechner/Servernamen ermitteln
Dim sIP As String
sIP = GetIPFromHost("vbarchiv.net")

' Rechner/Servername anhand IP ermitteln
Dim sHost As String
sHost = GetHostFromIP("192.168.0.1")

Anmerkung:
Das Ermitteln des Hostnamen anhand einer IP-Adresse kann ein paar Sekunden dauern.