PRB: "Permission Denied" Using WithEvents and DCOM on WIN95

• Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0 on the following platform: Win95

SYMPTOMS

Receiving Error 70: "Permission Denied."

CAUSE

The client application has referenced a remote server class using the keyword WithEvents. When the server attempts to raise an event to the remote client, it attempts to identify itself to the client before it can raise the event. Remote access is not being granted to the server; therefore, the error occurs.

RESOLUTION

You can enable a WIN95 DCOM client to receive remote events by adding "The World" user to the client machines default security group using DCOMCNFG.EXE and setting it to "Access Granted."

The DCOM configuration that needs to occur for an NT server (or workstation) to communicate with a Win95 client application is the following:

On the DCOM SERVER using DCOMCNFG.EXE:

1. Select the server ProgID or GUID.

2. Click Properties, select the Security Tab, and then make the following changes:

   CUSTOM ACCESS PERMISSIONS:

        Everyone  -allow access
        System     -allow access
        Interactive -allow access
   
      CUSTOM LAUNCH PERMISSIONS:
        Everyone  -allow launch
        System     -allow launch
        Interactive -allow launch
   
      CUSTOM CONFIGURATION PERMISSIONS:
        CREATOR-OWNER -full
        Everyone -read
        System -full
        Interactive -full
   
   

3. Select the Identity Tab, and then select "The Interactive User."

4. Click OK two times.

1. Using DCOMCNFG.EXE, select the Default Security Tab.

2. Click Edit Default and then grant Access to "The World" user.

STATUS

Microsoft is researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

As an alternative to using remote events, you can implement a callback to enable two-way communication between a DCOM client and server using Visual Basic 5.0.

For more information regarding callbacks, please see the following article in the Microsoft Knowledge Base:

      ARTICLE-ID: Q175510
      TITLE     : VB5DCOM.EXE: Using Callbacks and WithEvents with DCOM

Steps to Reproduce Behavior

1. Add the following code to the Declarations section of a standard form:

         Dim WithEvents MyServer as DCOMServer.EventClass
   

2. Add a CommandButton to the form and add the following code to it:

         Private Sub Command1_Click()
            Set MyServer = New DCOMServer.EventClass
            Call MyServer.TimerTask(9.84)
         End Sub
   
         Private Sub MyServer_UpdateTime(ByVal dblJump As Double)
         Dim ServerTime as String
            ServerTime = Str(Format(dblJump, "0"))
            DoEvents
         End Sub
   
         Private Sub MyServer_Complete()
            Set MyServer = Nothing
         End Sub
   
   

3. Close the client project and create the server project.

1. Start a new ActiveX exe project and set the name to "DCOMServer."

2. Add a class module and set the name property to EventClass.

3. Add the following code to the Declarations section of the EventClass:

         Public Event UpdateTime(ByVal dblJump As Double)
         Public Event Complete()
   

4. Add the following procedure to the EventClass class module:

         Public Sub TimerTask(ByVal Duration As Double)
         Dim dblStart As Double
         Dim dblSecond As Double
         Dim dblSoFar As Double
   

         dblStart = Timer
         dblSoFar = dblStart
         Do While Timer < dblStart + Duration
             If Timer - dblSoFar >= 1 Then
                  dblSoFar = dblSoFar + 1
                  RaiseEvent UpdateTime(Timer - dblStart)
             End If
         Loop
         RaiseEvent Complete
         End Sub
   
   

5. Compile and close the server project.

6. Reopen the client application and set a reference to the server "MyServer.EventClass" in Project References.

7. Run the client project and click on Command1. Note that you receive "Error 70 Permission Denied" when the server executes the line "RaiseEvent UpdateTime(Timer - dblStart)" in the TimerTask procedure.

REFERENCES

VB5DCOM.exe file in the Microsoft SoftWare Library.

For additional information, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q171456
   TITLE     : PRB: Run-time error -2147023071 (80070721) using WithEvents