LEARN MS-ACCESS TIPS AND TRICKS: Who is Online

Under Title Banner As we already knew we can install Access Database on a Local Area Network (LAN) and several Users can work on it at the same time. But it is difficult to know how many users are actually online with the Application at a given time.

Similarly, when there are several MS-Access Databases on a Network under a centrally controlled Security Workgroup it will be interesting to know which users are currently working on the MS-Access Applications on the Network.

You don’t need any complicated programs to find this out. When someone opens a Database, say NorthWind.mdb, MS-Access opens a Lock-File with the same name of the Database with file extension .ldb (Northwind.ldb) in the same folder of the Database. You can open this file with Notepad or any other Text Editor and view the contents.

This file contains the Workstation Ids and MS-Access User IDs of all the active Users of the Database. The lock file will be deleted by MS-Access when all the Users close the database. In other words if a Lock File is not active then nobody is currently using the database.

We can implement MS-Access Security of several Databases with a common Workgroup File in a Network holding Workgroup IDs, User IDs and User Passwords. In such situations there will be a common Workgroup File (a Database with .MDW extension) accessible to all the Users in a Network. When someone Log-in into the Workgroup to open a database, a lock-file with .ldb extension will open up with the same name of the Workgroup file. This file will contain the Workstation IDs and User IDs of all the Users currently active across different databases.

We will design a Form and write Programs to open the Lock-File of a Database or Workgroup File and display the List of Workstation IDs and User IDs currently active. In addition to that we will try to send messages through Network to the selected Users from this list.

Design a Form similar to the one shown below and change the Properties of the Controls as explained. Smaller controls are Text Boxes and the big Control under the label Users Online is a List Box.

Click on the Text Box below the label: Workgroup or Database File Path and display the property sheet. Change the value of the Name Property to FPath.

Display the Property Sheet of the List Box and change the value of the following properties as given below:

Name = UsrList

Row Source Type = Value List

Column Count = 2

Column Heads = No

Column Width = 1.25”;1.25”

Bound Column = 1

Multi Select = simple

Display the property sheet of the Text Box above the Send Message Button and change the value of the Name Property to msgtxt.

Display the Property Sheet of the Button with the caption <<Update User List and change the value of the Name Property to cmdUpdate.

Display the Property Sheet of the Button with the Caption Send Message and change the value of the Name property to cmdNS.

Save the Form with the name; whoisonline.

NB:

View

Code

whoisonline

NB:


Private Sub cmdNS_Click()
'-------------------------------------------------------
'Author: a.p.r. pillai
'Date  : 01/12/2007
'-------------------------------------------------------
Dim ctl As ListBox, msg As String, usrs As String
Dim i As Integer, pcs() As String, xmsg As String
Dim ic As Integer, j As Integer, lc As Integer

On Error GoTo cmdNS_Click_Err

xmsg = Nz(Me.msgtxt, "")

If Len(xmsg) = 0 Then
   MsgBox "Message Control is Empty.", , _
"cmdNS_Click()"
   Exit Sub
End If

Set ctl = Me.UsrList
lc = ctl.listcount
ic = ctl.ItemsSelected.Count

If ic > 0 Then
ReDim pcs(1 To ic, 1 To 2)
i = 0
For j = 0 To lc - 1
If ctl.Selected(j) Then
    i = i + 1
    pcs(i, 1) = ctl.Column(0, j)
    pcs(i, 2) = ctl.Column(1, j)
End If
Next

usrs = ""
For j = 1 To i
msg = "NET SEND " & pcs(j, 1) & " User: " & pcs(j, 2) & " " & xmsg
  Call Shell(msg)
  If Len(usrs) = 0 Then
     usrs = j & ". WorkStationID: " _
     & pcs(j, 1) & "  UserID: " & pcs(j, 2)
  Else
     usrs = usrs & vbCr & j & ". WorkStationID: " _
     & pcs(j, 1) & "  UserID: " & pcs(j, 2)
  End If
Next
  MsgBox "Messages Sent to:" & vbCr & vbCr _
  & usrs & vbCr & vbCr & "successfully.", , _
"cmdNS_Click()"
Else
  MsgBox "Select one or more Users in list and try again.", , _
 "cmdNS_Click()"
End If

cmdNS_Click_Exit:
Exit Sub

cmdNS_Click_Err:
MsgBox Err.Description, , "cmdNS_Click()"
Resume cmdNS_Click_Exit
End Sub



Private Sub cmdUpdate_Click()
    Me.UsrList.SetFocus
    Me.cmdUpdate.Enabled = False
   WhoisOnline Me.FPath
    Me.cmdUpdate.Enabled = True
End Sub

Copy and Paste the following VB Code into a Global Module in your Project and save:


Public Function WhoisOnline(ByVal strPathName)
Dim strldb() As String, j As Integer, strPath As String
Dim str As String, intlen As Integer, t As Date
Dim pos As Integer, xsize As Integer, l As Integer
Dim FRM As Form, ctl As ListBox, qt As String
Dim x As String

Const strlen As Integer = 62

On Error Resume Next

qt = Chr$(34)

strPath = Trim(Nz(strPathName, ""))

If Len(strPath) = 0 Then
  MsgBox "File Path is Empty.", , "WhoisOnline()"
  Exit Function
End If
  
str = Right(strPath, 4)
l = InStr(1, ".mdb.mdw.ldb", str)
Select Case l
    Case 0
       strPath = strPath & ".ldb"
    Case 1, 5
      strPath = Left(strPath, Len(strPath) - 4) & ".ldb"
    Case 9
       'it is .ldb no action
End Select

Set FRM = Forms("WhoisOnline")
Set ctl = FRM.Controls("UsrList")

Open "c:\x.bat" For Output As #1
Print #1, "@Echo off"
Print #1, "copy " & Chr$(34) & strPath & Chr$(34) & " c:\xx.txt"
Close #1

Call Shell("c:\x.bat", vbHide)

x=""
t=Timer
Do While Len(x) = 0 And Timer < (t + 5)
   x = Dir("c:\xx.txt")
Loop

t = Timer
Do While Timer < (t + 5)
   'do nothing
Loop

Open "c:\xx.txt" For Input As #1
If Err > 0 Then
  'Lock file copying was not successfull
  MsgBox "Database Lock File copy was not successful." _
  & " Increase the delay loop Value from 5 to 10 seconds and try again.", , "WhoisOnline()"
  Exit Function
End If
Input #1, str
Close #1

intlen = Int(Len(str) / strlen) + 1
ReDim strldb(1 To intlen, 1 To 2) As String
xsize = strlen / 2

For j = 1 To intlen
  pos = IIf(j = 1, 1, (j - 1) * strlen + 1)
  strldb(j, 1) = Trim(Mid(str, pos, xsize))
  pos = pos + strlen / 2
  strldb(j, 2) = Trim(Mid(str, pos, xsize))
Next

str = ""
For j = 1 To intlen
  If Len(str) = 0 Then
    str = qt & Trim(strldb(j, 1)) & qt & ";" & qt _
    & Trim(strldb(j, 2)) & qt
  Else
    str = str & ";" & qt & Trim(strldb(j, 1)) & qt _
    & ";" & qt & Trim(strldb(j, 2)) & qt
  End If
Next
ctl.RowSource = str
ctl.Requery

Kill "c:\x.bat"
Kill "c:\xx.txt"
End Function

c:\x.bat

c:\xx.txt

Open the whoisonline Form in Normal View. Type the full path of an active database (Tip: give the Path and Name of the Database you are currently working on, if you are not on a Network). If you are on a Network and have a common MS-Access Workgroup File, which other Users are currently connected then give that File’s Path and Name. No need to give File Name extensions .mdb, .mdw or .ldb, but if you wish to include you may do so for clarity.