Microsoft KB Archive/253140

= How To Use WTSEnumerateProcesses from Visual Basic =

Article ID: 253140

Article Last Modified on 9/2/2004

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APPLIES TO

 Microsoft Visual Basic 4.0 Professional Edition, when used with:  Microsoft Windows 2000 Standard Edition

 Microsoft Windows NT Server 4.0 Standard Edition

 Microsoft Windows NT Workstation 4.0 Developer Edition  Microsoft Visual Basic 5.0 Professional Edition, when used with:  Microsoft Windows 2000 Standard Edition</li></ul>

 Microsoft Windows NT Server 4.0 Standard Edition</li></ul>

 Microsoft Windows NT Workstation 4.0 Developer Edition</li></ul> </li> Microsoft Visual Basic 6.0 Professional Edition, when used with:  Microsoft Windows 2000 Standard Edition</li></ul>

 Microsoft Windows NT Server 4.0 Standard Edition</li></ul>

 Microsoft Windows NT Workstation 4.0 Developer Edition</li></ul> </li> Microsoft Visual Basic 4.0 Enterprise Edition, when used with:  Microsoft Windows 2000 Standard Edition</li></ul>

<ul> <li>Microsoft Windows NT Server 4.0 Standard Edition</li></ul>

<ul> <li>Microsoft Windows NT Workstation 4.0 Developer Edition</li></ul> </li> <li>Microsoft Visual Basic 5.0 Enterprise Edition, when used with: <ul> <li>Microsoft Windows 2000 Standard Edition</li></ul>

<ul> <li>Microsoft Windows NT Server 4.0 Standard Edition</li></ul>

<ul> <li>Microsoft Windows NT Workstation 4.0 Developer Edition</li></ul> </li> <li>Microsoft Visual Basic 6.0 Enterprise Edition, when used with: <ul> <li>Microsoft Windows 2000 Standard Edition</li></ul>

<ul> <li>Microsoft Windows NT Server 4.0 Standard Edition</li></ul>

<ul> <li>Microsoft Windows NT Workstation 4.0 Developer Edition</li></ul> </li></ul>

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This article was previously published under Q253140

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SUMMARY
The Microsoft Windows API WTSEnumerateProcesses function allows you to obtain information about the active processes running on a Terminal Server machine. This article includes an example of using this API function from Visual Basic.

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MORE INFORMATION
The WTSEnumerateProcesses function enumerates processes on a Terminal Server host. 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. In this example, a call to the WTSEnumerateProcesses function is used to retrieve the information. Once the information has been retrieved, it is displayed using a Listview control. Because you are using WTS_CURRENT_SERVER_HANDLE, the process information for the Terminal Server you are running the code on is retrieved. You can also retrieve process information for processes running on another Terminal Server computer. To do so, you can use the server handle returned from WTSOpenServer instead of WTS_CURRENT_SERVER_HANDLE.

Step-by-Step Example
<ol> <li>Start a new Visual Basic Standard EXE project. Form1 is created by default.</li> <li>Add a ListView control and CommandButton control to Form1.</li> <li> Add the following code to the General Declarations section of Form1: Option Explicit

Private Const WTS_CURRENT_SERVER_HANDLE = 0&

Private Type WTS_PROCESS_INFO SessionID As Long ProcessID As Long pProcessName As Long pUserSid As Long End Type

Private Declare Function WTSEnumerateProcesses _ Lib "wtsapi32.dll" Alias "WTSEnumerateProcessesA" _ (ByVal hServer As Long, ByVal Reserved As Long, _  ByVal Version As Long, ByRef ppProcessInfo 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 Sub Command1_Click GetWTSProcesses End Sub

Private Function GetStringFromLP(ByVal StrPtr As Long) As String Dim b As Byte Dim tempStr As String Dim bufferStr As String Dim Done As Boolean

Done = False Do     ' Get the byte/character that StrPtr is pointing to. CopyMemory b, ByVal StrPtr, 1 If b = 0 Then ' If you've found a null character, then you're done. Done = True Else tempStr = Chr$(b) ' Get the character for the byte's value bufferStr = bufferStr & tempStr 'Add it to the string StrPtr = StrPtr + 1 ' Increment the pointer to next byte/char End If  Loop Until Done GetStringFromLP = bufferStr End Function

Private Sub Form_Load ListView1.View = lvwReport Command1.Caption = "Refresh"

'Add the Column Headers for your ListView Control ListView1.ColumnHeaders.Add 1, "SessionID", "Session ID" ListView1.ColumnHeaders.Add 2, "ProcessID", "Process ID" ListView1.ColumnHeaders.Add 3, "ProcessName", "Process Name" ListView1.ColumnHeaders.Add 4, "UserID", "User ID"

GetWTSProcesses End Sub

Private Sub ListView1_ColumnClick(ByVal ColumnHeader As _                                 MSComctlLib.ColumnHeader) ' When a ColumnHeader object is clicked, the ListView control is ' sorted by the subitems of that column. ' Set the SortKey to the Index of the ColumnHeader - 1 ListView1.SortKey = ColumnHeader.Index - 1 ' Set Sorted to True to sort the list. ListView1.Sorted = True End Sub

Private Sub GetWTSProcesses Dim RetVal As Long Dim Count As Long Dim i As Integer Dim lpBuffer As Long Dim p As Long Dim udtProcessInfo As WTS_PROCESS_INFO Dim itmAdd As ListItem

ListView1.ListItems.Clear RetVal = WTSEnumerateProcesses(WTS_CURRENT_SERVER_HANDLE, _                                 0&, _                                  1, _                                  lpBuffer, _                                  Count) If RetVal Then ' WTSEnumerateProcesses was successful p = lpBuffer For i = 1 To Count ' Count is the number of Structures in the buffer ' WTSEnumerateProcesses returns a pointer, so copy it to a ' WTS_PROCESS_INO UDT so you can access its members CopyMemory udtProcessInfo, ByVal p, LenB(udtProcessInfo) ' Add items to the ListView control Set itmAdd = ListView1.ListItems.Add(i,, _                    CStr(udtProcessInfo.SessionID)) itmAdd.SubItems(1) = CStr(udtProcessInfo.ProcessID) ' Since pProcessName contains a pointer, call GetStringFromLP to get the ' variable length string it points to        itmAdd.SubItems(2) = GetStringFromLP(udtProcessInfo.pProcessName) itmAdd.SubItems(3) = CStr(udtProcessInfo.pUserSid)

' Increment to next WTS_PROCESS_INO structure in the buffer p = p + LenB(udtProcessInfo) Next i

Set itmAdd = Nothing WTSFreeMemory lpBuffer  'Free your memory buffer Else ' Error occurred calling WTSEnumerateProcesses ' Check Err.LastDllError for error code MsgBox "Error occurred calling WTSEnumerateProcesses. " & _ "Check the Platform SDK error codes in the MSDN Documentation" _ & " for more information.", vbCritical, "Error " & Err.LastDllError End If End Sub </li> <li>Run the project, and note that the ListView control is populated with the state of the processes currently running on the Terminal Server computer.</li> <li>Click the Refresh button to refresh the list.</li></ol>

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