Article: Q291789
Product(s): Microsoft Visual Basic for Windows
Version(s): 4.0,5.0,6.0
Operating System(s):
Keyword(s): kbAPI kbOSWinNT400 kbOSWin2000 kbSDKWin32 kbService kbVBp kbVBp500 kbVBp600 kbGrpDSVB k
Last Modified: 17-DEC-2001
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0, used with:
- the operating system: Microsoft Windows 2000
- the operating system: Microsoft Windows NT 4.0
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0, used with:
- the operating system: Microsoft Windows 2000
- the operating system: Microsoft Windows NT 4.0
-------------------------------------------------------------------------------
SUMMARY
=======
This article includes a code sample that demonstrates how to use the
WTSEnumerateSessions Terminal Server function from Visual Basic.
MORE INFORMATION
================
The WTSEnumerateSessions function is used to retrieve session information on a
Terminal Server. As a result, it requires Windows 2000 Server that is running
Terminal Services or Windows NT 4.0 Service Pack 4 (SP4) or later, Terminal
Server Edition. This sample enumerates the sessions on a specified Terminal
Server and displays the information in the Immediate window of the Visual Basic
Integrated Development Environment (IDE).
You can use the WTSEnumerateSessions function to retrieve the session ID,
computer name, and session state. The code sample queries the Terminal Server
computer that the code runs on, but it can be modified to query sessions that
are running on other Terminal Servers. You must have Query Information
permission to query a Terminal Server. For more information, see the MSDN
documentation in the "References" section.
Step-by-Step Example
--------------------
1. Create a new Standard EXE project in Visual Basic. Form1 is created by
default.
2. Add a CommandButton control (Command1) to Form1.
3. Paste the following code into the code window of Form1:
Option Explicit
Private Const WTS_CURRENT_SERVER_HANDLE = 0&
Private Enum WTS_CONNECTSTATE_CLASS
WTSActive
WTSConnected
WTSConnectQuery
WTSShadow
WTSDisconnected
WTSIdle
WTSListen
WTSReset
WTSDown
WTSInit
End Enum
Private Type WTS_SESSION_INFO
SessionID As Long
pWinStationName As Long
state As WTS_CONNECTSTATE_CLASS
End Type
Private Declare Function WTSEnumerateSessions _
Lib "wtsapi32.dll" Alias "WTSEnumerateSessionsA" ( _
ByVal hServer As Long, ByVal Reserved As Long, _
ByVal Version As Long, ByRef ppSessionInfo As Long, _
ByRef pCount As Long _
) As Long
Private Declare Sub WTSFreeMemory Lib "wtsapi32.dll" ( _
ByVal pMemory As Long)
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
Destination As Any, Source As Any, ByVal length As Long)
Private Declare Function lstrlenA Lib "kernel32" ( _
ByVal lpString As String) As Long
Private Declare Function lstrcpy Lib "kernel32" Alias "lstrcpyA" ( _
ByVal lpString1 As String, ByVal lpString2 As Long) As Long
Private arrWTSSessions() As WTS_SESSION_INFO
Private Function GetWTSSessions() As WTS_SESSION_INFO()
Dim RetVal As Long
Dim lpBuffer As Long
Dim Count As Long
Dim p As Long
Dim i As Integer
Dim arrSessionInfo() As WTS_SESSION_INFO
RetVal = WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, _
0&, _
1, _
lpBuffer, _
Count)
If RetVal Then
' WTSEnumerateProcesses was successful.
p = lpBuffer
ReDim arrSessionInfo(Count - 1)
CopyMemory arrSessionInfo(0), ByVal p, _
Count * LenB(arrSessionInfo(0))
' Free the memory buffer.
WTSFreeMemory lpBuffer
Else
' Error occurred calling WTSEnumerateProcesses.
' Check Err.LastDllError for error code.
MsgBox "An error occurred calling WTSEnumerateProcesses. " & _
"Check the Platform SDK error codes in the MSDN Documentation " & _
"for more information.", vbCritical, "ERROR " & Err.LastDllError
End If
GetWTSSessions = arrSessionInfo
End Function
Private Sub Command1_Click()
Dim CONNECTSTATE As WTS_CONNECTSTATE_CLASS
Dim i As Integer
arrWTSSessions = GetWTSSessions
For i = LBound(arrWTSSessions) To UBound(arrWTSSessions)
Debug.Print "Session ID: " & arrWTSSessions(i).SessionID
Debug.Print "Machine Name: " & _
PointerToStringA(arrWTSSessions(i).pWinStationName)
Debug.Print "***********"
Next i
End Sub
Public Function PointerToStringA(ByVal lpStringA As Long) As String
Dim nLen As Long
Dim sTemp As String
Dim lRet As Long
If lpStringA Then
nLen = lstrlenA(ByVal lpStringA)
If nLen Then
sTemp = String(nLen + 1, vbNullChar)
lstrcpy sTemp, ByVal lpStringA
PointerToStringA = sTemp
End If
End If
End Function
4. Press the F5 key to run the project.
5. Make sure that the Immediate window is open. If not, press CTRL+G to open it.
Click Command1. The session information is displayed in the Immediate window.
REFERENCES
==========
For more information about the WTSEnumerateSessions function, see the following
MSDN Web site:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/termserv/tsref_0h6b.asp
For additional information, click the article numbers below to view the articles
in the Microsoft Knowledge Base:
Q253140 HOWTO: Use WTSEnumerateProcesses from Visual Basic
Q190000 HOWTO: Get Started Programming with the Windows API (LONG)
Additional query words: Terminal Services TS Server
======================================================================
Keywords : kbAPI kbOSWinNT400 kbOSWin2000 kbSDKWin32 kbService kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport kbTermServ
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2
Version : :4.0,5.0,6.0
Issue type : kbhowto
=============================================================================