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API Home » Network » gethostbyname

gethostbyname

Category: Network
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API Explanation
The Windows Sockets gethostbyname function retrieves host information corresponding to a host name from a host database.

Parameter Information
Declare Function gethostbyname Lib "WSOCK32" (ByVal szHost As String) As Long

name
[out] A pointer to the null-terminated name of the host to resolve.

If no error occurs, gethostbyname returns a pointer to the HOSTENT structure described above. Otherwise, it returns a NULL pointer and a specific error number can be retrieved by calling WSAGetLastError.
Code



'In a form
Private Sub Form_Load()
MsgBox "IP-address: " + GetIPAddress
End Sub

'In a module
Public Const MIN_SOCKETS_REQD As Long = 1
Public Const WS_VERSION_REQD As Long = &H101
Public Const WS_VERSION_MAJOR As Long = WS_VERSION_REQD \\ &H100 And &HFF&
Public Const WS_VERSION_MINOR As Long = WS_VERSION_REQD And &HFF&
Public Const SOCKET_ERROR As Long = -1
Public Const WSADESCRIPTION_LEN = 257
Public Const WSASYS_STATUS_LEN = 129
Public Const MAX_WSADescription = 256
Public Const MAX_WSASYSStatus = 128

Public 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

Type WSADataInfo
wVersion As Integer
wHighVersion As Integer
szDescription As String * WSADESCRIPTION_LEN
szSystemStatus As String * WSASYS_STATUS_LEN
iMaxSockets As Integer
iMaxUdpDg As Integer
lpVendorInfo As String
End Type

Public Type HOSTENT
hName As Long
hAliases As Long
hAddrType As Integer
hLen As Integer
hAddrList As Long
End Type


Declare Function WSAStartupInfo Lib "WSOCK32" Alias "WSAStartup" (ByVal wVersionRequested As Integer, lpWSADATA As WSADataInfo) As Long
Declare Function WSACleanup Lib "WSOCK32" () As Long
Declare Function WSAGetLastError Lib "WSOCK32" () As Long
Declare Function WSAStartup Lib "WSOCK32" (ByVal wVersionRequired As Long, lpWSADATA As WSAData) As Long
Declare Function gethostname Lib "WSOCK32" (ByVal szHost As String, ByVal dwHostLen As Long) As Long
Declare Function gethostbyname Lib "WSOCK32" (ByVal szHost As String) As Long
Declare Sub CopyMemoryIP Lib "kernel32" Alias "RtlMoveMemory" (hpvDest As Any, ByVal hpvSource As Long, ByVal cbCopy As Long)

Public Function GetIPAddress() As String
Dim sHostName As String * 256
Dim lpHost As Long
Dim HOST As HOSTENT
Dim dwIPAddr As Long
Dim tmpIPAddr() As Byte
Dim I As Integer
Dim sIPAddr As String
If Not SocketsInitialize() Then
GetIPAddress = ""
Exit Function
End If
If gethostname(sHostName, 256) = SOCKET_ERROR Then
GetIPAddress = ""
MsgBox "Windows Sockets error " & Str$(WSAGetLastError()) & " has occurred. Unable to successfully get Host Name."
SocketsCleanup
Exit Function
End If
sHostName = Trim$(sHostName)
lpHost = gethostbyname(sHostName)
If lpHost = 0 Then
GetIPAddress = ""
MsgBox "Windows Sockets are not responding. " & "Unable to successfully get Host Name."
SocketsCleanup
Exit Function
End If
CopyMemoryIP HOST, lpHost, Len(HOST)
CopyMemoryIP dwIPAddr, HOST.hAddrList, 4
ReDim tmpIPAddr(1 To HOST.hLen)
CopyMemoryIP tmpIPAddr(1), dwIPAddr, HOST.hLen
For I = 1 To HOST.hLen
sIPAddr = sIPAddr & tmpIPAddr(I) & "."
Next
GetIPAddress = Mid$(sIPAddr, 1, Len(sIPAddr) - 1)
SocketsCleanup
End Function

Public Function GetIPHostName() As String
Dim sHostName As String * 256
If Not SocketsInitialize() Then
GetIPHostName = ""
Exit Function
End If
If gethostname(sHostName, 256) = SOCKET_ERROR Then
GetIPHostName = ""
MsgBox "Windows Sockets error " & Str$(WSAGetLastError()) & _
" has occurred. Unable to successfully get Host Name."
SocketsCleanup
Exit Function
End If
GetIPHostName = Left$(sHostName, InStr(sHostName, Chr(0)) - 1)
SocketsCleanup
End Function

Public Function HiByte(ByVal wParam As Integer)
HiByte = wParam \\ &H100 And &HFF&
End Function

Public Function LoByte(ByVal wParam As Integer)
LoByte = wParam And &HFF&
End Function

Public Sub SocketsCleanup()
If WSACleanup() <> ERROR_SUCCESS Then
MsgBox "Socket error occurred in Cleanup."
End If
End Sub

Public Function SocketsInitialize() As Boolean
Dim WSAD As WSAData
Dim sLoByte As String
Dim sHiByte As String
If WSAStartup(WS_VERSION_REQD, WSAD) <> ERROR_SUCCESS Then
MsgBox "The 32-bit Windows Socket is not responding."
SocketsInitialize = False
Exit Function
End If
If WSAD.wMaxSockets < MIN_SOCKETS_REQD Then
MsgBox "This application requires a minimum of " & CStr(MIN_SOCKETS_REQD) & " supported sockets."
SocketsInitialize = False
Exit Function
End If
If LoByte(WSAD.wVersion) < WS_VERSION_MAJOR Or (LoByte(WSAD.wVersion) = _
WS_VERSION_MAJOR And HiByte(WSAD.wVersion) < WS_VERSION_MINOR) Then
sHiByte = CStr(HiByte(WSAD.wVersion))
sLoByte = CStr(LoByte(WSAD.wVersion))
MsgBox "Sockets version " & sLoByte & "." & sHiByte & " is not supported by 32-bit Windows Sockets."
SocketsInitialize = False
Exit Function
End If
'must be OK, so lets do it
SocketsInitialize = True
End Function






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