| Prerequisites |
| DHCP IP address. |
|
|
 I have a page at http://vbnet.mvps.org/resources/tools/getpublicip.shtml that can be used by anyone to return their public IP address. When viewed in a browser the page shows only the IP with no other text making scraping the page easier than those containing other information. Using the fast and transparent URLDownloadToFile API the resulting file has a bit of html and java code in it which requires parsing, and is the subject of this demo.
Essentially the code uses the familiar UrlDownloadToFile call, with a DeleteUrlCacheEntry call for good measure, to retrieve the file to a local file path, where it is loaded into a buffer and parsed to extract the IP address string embedded in the file. All pretty straightforward, this is really the only mechanism available to identify the public IP address on machines served a DHCP address by their DSL router.
|
| |
| BAS Module Code |
| None. |
|
| |
| Form Code |
 |
| Drop a command button (Command1), and two text boxes (Text1 and Text2) onto a form along with the following code. The labels shown are optional. |
|
Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright ©1996-2006 VBnet, Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
' applications, but you may not reproduce
' or publish this code on any web site,
' online service, or distribute as source
' on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Const ERROR_SUCCESS As Long = 0
Private Const MAX_ADAPTER_NAME_LENGTH As Long = 256
Private Const MAX_ADAPTER_DESCRIPTION_LENGTH As Long = 128
Private Const MAX_ADAPTER_ADDRESS_LENGTH As Long = 8
Private Type IP_ADDRESS_STRING
IpAddr(0 To 15) As Byte
End Type
Private Type IP_MASK_STRING
IpMask(0 To 15) As Byte
End Type
Private Type IP_ADDR_STRING
dwNext As Long
IpAddress As IP_ADDRESS_STRING
IpMask As IP_MASK_STRING
dwContext As Long
End Type
Private Type IP_ADAPTER_INFO
dwNext As Long
ComboIndex As Long 'reserved
sAdapterName(0 To (MAX_ADAPTER_NAME_LENGTH + 3)) As Byte
sDescription(0 To (MAX_ADAPTER_DESCRIPTION_LENGTH + 3)) As Byte
dwAddressLength As Long
sIPAddress(0 To (MAX_ADAPTER_ADDRESS_LENGTH - 1)) As Byte
dwIndex As Long
uType As Long
uDhcpEnabled As Long
CurrentIpAddress As Long
IpAddressList As IP_ADDR_STRING
GatewayList As IP_ADDR_STRING
DhcpServer As IP_ADDR_STRING
bHaveWins As Long
PrimaryWinsServer As IP_ADDR_STRING
SecondaryWinsServer As IP_ADDR_STRING
LeaseObtained As Long
LeaseExpires As Long
End Type
Private Declare Function GetAdaptersInfo Lib "iphlpapi.dll" _
(pTcpTable As Any, _
pdwSize As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" _
Alias "RtlMoveMemory" _
(dst As Any, _
src As Any, _
ByVal bcount As Long)
Private Declare Function URLDownloadToFile Lib "urlmon" _
Alias "URLDownloadToFileA" _
(ByVal pCaller As Long, _
ByVal szURL As String, _
ByVal szFileName As String, _
ByVal dwReserved As Long, _
ByVal lpfnCB As Long) As Long
Private Declare Function DeleteUrlCacheEntry Lib "Wininet.dll" _
Alias "DeleteUrlCacheEntryA" _
(ByVal lpszUrlName As String) As Long
Private Declare Function lstrlenW Lib "kernel32" _
(ByVal lpString As Long) As Long
Private Sub Form_Load()
Command1.Caption = "Get Public IP"
Text1.Text = LocalIPAddress()
Text2.Text = ""
End Sub
Private Sub Command1_Click()
Text2.Text = GetPublicIP()
End Sub
Private Function GetPublicIP()
Dim sSourceUrl As String
Dim sLocalFile As String
Dim hfile As Long
Dim buff As String
Dim pos1 As Long
Dim pos2 As Long
'site returning IP address
sSourceUrl = "http://vbnet.mvps.org/resources/tools/getpublicip.shtml"
sLocalFile = "c:\ip.txt"
'ensure this file does not exist in the cache
Call DeleteUrlCacheEntry(sSourceUrl)
'download the public IP file,
'read into a buffer and delete
If DownloadFile(sSourceUrl, sLocalFile) Then
hfile = FreeFile
Open sLocalFile For Input As #hfile
buff = Input$(LOF(hfile), hfile)
Close #hfile
'look for the IP line
pos1 = InStr(buff, "var ip =")
'if found,
If pos1 Then
'get position of first and last single
'quotes around address (e.g. '11.22.33.44')
pos1 = InStr(pos1 + 1, buff, "'", vbTextCompare) + 1
pos2 = InStr(pos1 + 1, buff, "'", vbTextCompare) '- 1
'return the IP address
GetPublicIP = Mid$(buff, pos1, pos2 - pos1)
Else
GetPublicIP = "(unable to parse IP)"
End If 'pos1
Kill sLocalFile
Else
GetPublicIP = "(unable to access shtml page)"
End If 'DownloadFile
End Function
Private Function DownloadFile(ByVal sURL As String, _
ByVal sLocalFile As String) As Boolean
DownloadFile = URLDownloadToFile(0, sURL, sLocalFile, 0, 0) = ERROR_SUCCESS
End Function
Private Function LocalIPAddress() As String
Dim cbRequired As Long
Dim buff() As Byte
Dim ptr1 As Long
Dim sIPAddr As String
Dim Adapter As IP_ADAPTER_INFO
Call GetAdaptersInfo(ByVal 0&, cbRequired)
If cbRequired > 0 Then
ReDim buff(0 To cbRequired - 1) As Byte
If GetAdaptersInfo(buff(0), cbRequired) = ERROR_SUCCESS Then
'get a pointer to the data stored in buff()
ptr1 = VarPtr(buff(0))
Do While (ptr1 <> 0)
'copy the data from the pointer to the
'first adapter into the IP_ADAPTER_INFO type
CopyMemory Adapter, ByVal ptr1, LenB(Adapter)
With Adapter
'the DHCP IP address is in the
'IpAddress.IpAddr member
sIPAddr = TrimNull(StrConv(.IpAddressList.IpAddress.IpAddr, vbUnicode))
If Len(sIPAddr) > 0 Then Exit Do
ptr1 = .dwNext
End With 'With Adapter
'ptr1 is 0 when (no more adapters)
Loop 'Do While (ptr1 <> 0)
End If 'If GetAdaptersInfo
End If 'If cbRequired > 0
'return any string found
LocalIPAddress = sIPAddr
End Function
Private Function TrimNull(startstr As String) As String
TrimNull = Left$(startstr, lstrlenW(StrPtr(startstr)))
End Function
|
|
