Q160215: HOWTO: Obtain the Host IP Address Using Windows Sockets
Article: Q160215
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:4.0,5.0,6.0
Operating System(s):
Keyword(s): kbVBp kbVBp400 kbVBp500 kbVBp600
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0
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SUMMARY
=======
This article demonstrates how to obtain the host IP address of the local machine
by using the GetHostByName API of the Windows Sockets dll, Wsock32.dll. To
obtain the host IP address, you must use GetHostByName in conjunction with
GetHostName.
MORE INFORMATION
================
GetHostName returns the standard host name for the local machine. You can use
GetHostByName to resolve this name and return a pointer to the HOSTENT
structure. This structure contains the host address information.
Step-by-Step Example
--------------------
1. Start a new project in Visual Basic. Form1 is created by default.
2. Place a CommandButton, Command1, on Form1.
3. Place the following code in the General Declarations section of Form1:
Private Const WS_VERSION_REQD = &H101
Private Const WS_VERSION_MAJOR = WS_VERSION_REQD \ &H100 And &HFF&
Private Const WS_VERSION_MINOR = WS_VERSION_REQD And &HFF&
Private Const MIN_SOCKETS_REQD = 1
Private Const SOCKET_ERROR = -1
Private Const WSADescription_Len = 256
Private 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 WSAGetLastError Lib "WSOCK32.DLL" () As Long
Private Declare Function WSAStartup Lib "WSOCK32.DLL" (ByVal _
wVersionRequired as Integer, lpWSAData As WSADATA) As Long
Private Declare Function WSACleanup Lib "WSOCK32.DLL" () As Long
Private Declare Function gethostname Lib "WSOCK32.DLL" (ByVal hostname$,_
ByVal HostLen as Long) as long
Private Declare Function gethostbyname Lib "WSOCK32.DLL" (ByVal _
hostname$) As Long
Private Declare Sub RtlMoveMemory Lib "KERNEL32" (hpvDest As Any, ByVal_
hpvSource&, ByVal cbCopy&)
Function hibyte(ByVal wParam As Integer)
hibyte = wParam \ &H100 And &HFF&
End Function
Function lobyte(ByVal wParam As Integer)
lobyte = wParam And &HFF&
End Function
Sub SocketsInitialize()
Dim WSAD As WSADATA
Dim iReturn As Integer
Dim sLowByte As String, sHighByte As String, sMsg As String
iReturn = WSAStartup(WS_VERSION_REQD, WSAD)
If iReturn <> 0 Then
MsgBox "Winsock.dll is not responding."
End
End If
If lobyte(WSAD.wversion) <WS_VERSION_MAJOR Or (lobyte(WSAD.wversion) = _
WS_VERSION_MAJOR And hibyte(WSAD.wversion) < WS_VERSION_MINOR) Then
sHighByte = Trim$(Str$(hibyte(WSAD.wversion)))
sLowByte = Trim$(Str$(lobyte(WSAD.wversion)))
sMsg = "Windows Sockets version " & sLowByte & "." & sHighByte
sMsg = sMsg & " is not supported by winsock.dll "
MsgBox sMsg
End
End If
'iMaxSockets is not used in winsock 2. So the following check is only
'necessary for winsock 1. If winsock 2 is requested,
'the following check can be skipped.
If WSAD.iMaxSockets < MIN_SOCKETS_REQD Then
sMsg = "This application requires a minimum of "
sMsg = sMsg & Trim$(Str$(MIN_SOCKETS_REQD)) & " supported sockets."
MsgBox sMsg
End
End If
End Sub
Sub SocketsCleanup()
Dim lReturn As Long
lReturn = WSACleanup()
If lReturn <> 0 Then
MsgBox "Socket error " & Trim$(Str$(lReturn)) & " occurred in Cleanup "
End
End If
End Sub
Sub Form_Load()
SocketsInitialize
End Sub
Private Sub Form_Unload(Cancel As Integer)
SocketsCleanup
End Sub
Private Sub Command1_click()
Dim hostname As String * 256
Dim hostent_addr As Long
Dim host As HOSTENT
Dim hostip_addr As Long
Dim temp_ip_address() As Byte
Dim i As Integer
Dim ip_address As String
If gethostname(hostname, 256) = SOCKET_ERROR Then
MsgBox "Windows Sockets error " & Str(WSAGetLastError())
Exit Sub
Else
hostname = Trim$(hostname)
End If
hostent_addr = gethostbyname(hostname)
If hostent_addr = 0 Then
MsgBox "Winsock.dll is not responding."
Exit Sub
End If
RtlMoveMemory host, hostent_addr, LenB(host)
RtlMoveMemory hostip_addr, host.hAddrList, 4
MsgBox hostname
'get all of the IP address if machine is multi-homed
Do
ReDim temp_ip_address(1 To host.hLength)
RtlMoveMemory temp_ip_address(1), hostip_addr, host.hLength
For i = 1 To host.hLength
ip_address = ip_address & temp_ip_address(i) & "."
Next
ip_address = Mid$(ip_address, 1, Len(ip_address) - 1)
MsgBox ip_address
ip_address = ""
host.hAddrList = host.hAddrList + LenB(host.hAddrList)
RtlMoveMemory hostip_addr, host.hAddrList, 4
Loop While (hostip_addr <> 0)
End Sub
4. Press the F5 key to run the project.
5. Click Command1 to obtain the host information.
REFERENCES
==========
For additional information, please see the following article in the Microsoft
Knowledge Base:
Q154512 SAMPLE: WINSOCK.EXE: Getting HostAddress Using Windows Sockets
Additional query words:
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Keywords : kbVBp kbVBp400 kbVBp500 kbVBp600
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400
Version : WINDOWS:4.0,5.0,6.0
Issue type : kbhowto
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