Visual Basic Network Services
NetServerEnum: Obtain Domain/Workgroup Servers and Machines
     
Posted:   Tuesday May 22, 2001
Updated:   Monday December 26, 2011
     
Applies to:   VB4-32, VB5, VB6
Developed with:   VB6, Windows 2000
OS restrictions:   Windows NT3.1, Windows NT4, Windows 2000, Windows XP
Author:   VBnet - Randy Birch
     

Related:  

NetServerEnum: Get Version Info for Domain/Workgroup Servers and Machines
NetServerGetInfo: Configuration Info for Domain/Workgroup Servers and Machines
     
 Prerequisites
One of the operating systems listed under OS Restrictions above.

NetServerEnum returns, dependant on the bit mask specified, servers and/or machines that are visible on the local domain, bit masks can be combined using Or to produce a customized listing more suitable to specific needs. No special group membership is required to successfully execute the NetServerEnum function.

NetServerEnum, depending on the data level passed, returns only minimal information about each connected machine. Extended information for specific servers can be obtained using the WNetEnumResource function instead.

The illustration shows the two machines on my local network, imaginatively named.

 BAS Module Code
None.

 Form Code
To a form add a command button (Command1) and list box (List1). Add the following to the form:

Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright 1996-2011 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.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'Windows type used to call the Net API
Private Const MAX_PREFERRED_LENGTH As Long = -1
Private Const NERR_SUCCESS As Long = 0&
Private Const ERROR_MORE_DATA As Long = 234&

Private Const SV_TYPE_WORKSTATION         As Long = &H1
Private Const SV_TYPE_SERVER              As Long = &H2
Private Const SV_TYPE_SQLSERVER           As Long = &H4
Private Const SV_TYPE_DOMAIN_CTRL         As Long = &H8
Private Const SV_TYPE_DOMAIN_BAKCTRL      As Long = &H10
Private Const SV_TYPE_TIME_SOURCE         As Long = &H20
Private Const SV_TYPE_AFP                 As Long = &H40
Private Const SV_TYPE_NOVELL              As Long = &H80
Private Const SV_TYPE_DOMAIN_MEMBER       As Long = &H100
Private Const SV_TYPE_PRINTQ_SERVER       As Long = &H200
Private Const SV_TYPE_DIALIN_SERVER       As Long = &H400
Private Const SV_TYPE_XENIX_SERVER        As Long = &H800
Private Const SV_TYPE_SERVER_UNIX         As Long = SV_TYPE_XENIX_SERVER
Private Const SV_TYPE_NT                  As Long = &H1000
Private Const SV_TYPE_WFW                 As Long = &H2000
Private Const SV_TYPE_SERVER_MFPN         As Long = &H4000
Private Const SV_TYPE_SERVER_NT           As Long = &H8000
Private Const SV_TYPE_POTENTIAL_BROWSER   As Long = &H10000
Private Const SV_TYPE_BACKUP_BROWSER      As Long = &H20000
Private Const SV_TYPE_MASTER_BROWSER      As Long = &H40000
Private Const SV_TYPE_DOMAIN_MASTER       As Long = &H80000
Private Const SV_TYPE_SERVER_OSF          As Long = &H100000
Private Const SV_TYPE_SERVER_VMS          As Long = &H200000
Private Const SV_TYPE_WINDOWS             As Long = &H400000  'Windows95 and above
Private Const SV_TYPE_DFS                 As Long = &H800000  'Root of a DFS tree
Private Const SV_TYPE_CLUSTER_NT          As Long = &H1000000 'NT Cluster
Private Const SV_TYPE_TERMINALSERVER      As Long = &H2000000 'Terminal Server
Private Const SV_TYPE_DCE                 As Long = &H10000000'IBM DSS
Private Const SV_TYPE_ALTERNATE_XPORT     As Long = &H20000000'rtn alternate transport
Private Const SV_TYPE_LOCAL_LIST_ONLY     As Long = &H40000000'rtn local only
Private Const SV_TYPE_DOMAIN_ENUM         As Long = &H80000000
Private Const SV_TYPE_ALL                 As Long = &HFFFFFFFF

Private Const SV_PLATFORM_ID_OS2       As Long = 400
Private Const SV_PLATFORM_ID_NT        As Long = 500

'Mask applied to svX_version_major in
'order to obtain the major version number.
Private Const MAJOR_VERSION_MASK        As Long = &HF

Private Type SERVER_INFO_100
  sv100_platform_id As Long
  sv100_name As Long
End Type

Private Declare Function NetServerEnum Lib "netapi32" _
  (ByVal servername As Long, _
   ByVal level As Long, _
   buf As Any, _
   ByVal prefmaxlen As Long, _
   entriesread As Long, _
   totalentries As Long, _
   ByVal servertype As Long, _
   ByVal domain As Long, _
   resume_handle As Long) As Long

Private Declare Function NetApiBufferFree Lib "netapi32" _
   (ByVal Buffer As Long) As Long

Private Declare Sub CopyMemory Lib "kernel32" _
   Alias "RtlMoveMemory" _
  (pTo As Any, uFrom As Any, _
   ByVal lSize As Long)
   
Private Declare Function lstrlenW Lib "kernel32" _
  (ByVal lpString As Long) As Long   


Private Sub Form_Load()

   Command1.Caption = "Net Server Enum"

End Sub
   

Private Sub Command1_Click()

   Call GetServers(vbNullString)
 
End Sub


Private Function GetServers(sDomain As String) As Long

  'lists all servers of the specified type
  'that are visible in a domain.
  
   Dim bufptr          As Long
   Dim dwEntriesread   As Long
   Dim dwTotalentries  As Long
   Dim dwResumehandle  As Long
   Dim se100           As SERVER_INFO_100
   Dim success         As Long
   Dim nStructSize     As Long
   Dim cnt             As Long

   nStructSize = LenB(se100)
   
  'Call passing MAX_PREFERRED_LENGTH to have the
  'API allocate required memory for the return values.
  '
  'The call is enumerating all machines on the
  'network (SV_TYPE_ALL); however, by Or'ing
  'specific bit masks for defined types you can
  'customize the returned data. For example, a
  'value of 0x00000003 combines the bit masks for
  'SV_TYPE_WORKSTATION (0x00000001) and
  'SV_TYPE_SERVER (0x00000002).
  '
  'dwServerName must be Null. The level parameter
  '(100 here) specifies the data structure being
  'used (in this case a SERVER_INFO_100 structure).
  '
  'The domain member is passed as Null, indicating
  'machines on the primary domain are to be retrieved.
  'If you decide to use this member, pass
  'StrPtr("domain name"), not the string itself.
   success = NetServerEnum(0&, _
                           100, _
                           bufptr, _
                           MAX_PREFERRED_LENGTH, _
                           dwEntriesread, _
                           dwTotalentries, _
                           SV_TYPE_ALL, _
                           0&, _
                           dwResumehandle)

  'if all goes well
   If success = NERR_SUCCESS Then
      
    'loop through the returned data, adding each
    'machine to the list
      For cnt = 0 To dwEntriesread - 1
         
        'get one chunk of data and cast
        'into an SERVER_INFO_100 struct
        'in order to add the name to a list
         CopyMemory se100, ByVal bufptr + (nStructSize * cnt), nStructSize
            
         List1.AddItem GetPointerToByteStringW(se100.sv100_name)
         
      Next
      
   End If
   
  'clean up regardless of success
   Call NetApiBufferFree(bufptr)
   
  'return entries as sign of success 
   GetServers = dwEntriesread 

End Function


Public Function GetPointerToByteStringW(ByVal dwData As Long) As String
  
   Dim tmp() As Byte
   Dim tmplen As Long
   
   If dwData <> 0 Then
   
      tmplen = lstrlenW(dwData) * 2
      
      If tmplen <> 0 Then
      
         ReDim tmp(0 To (tmplen - 1)) As Byte
         CopyMemory tmp(0), ByVal dwData, tmplen
         GetPointerToByteStringW = tmp
         
     End If
     
   End If
    
End Function
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