How To Use WTSEnumerateProcesses from Visual Basic (253140)

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

1. Start a new Visual Basic Standard EXE project. Form1 is created by default.
2. Add a ListView control and CommandButton control to Form1.
3. 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
   					

4. Run the project, and note that the ListView control is populated with the state of the processes currently running on the Terminal Server computer.
5. Click the Refresh button to refresh the list.