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VB5 handling user messages from other apps

Posted on 1997-11-20
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Last Modified: 2008-02-26
I have a visual c++(5.0) app that needs to send a message to a visual basic(5.0) app for processing.  Is it possible for me to direct the message to the correct vb function through a message-map?  Is DDE an option?  I have been told that DDE is being avoided and OLE is the standard.  I am trying to avoid making the c++ project an OLE object.  What is the recommended solution for interprocess communication from a c++ app to a vb app without registering the object?
Getting the WM_COPYDATA message to work would be sufficient.
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Question by:crl
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8 Comments
 

Author Comment

by:crl
ID: 1441657
Edited text of question
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Author Comment

by:crl
ID: 1441658
Adjusted points to 150
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Accepted Solution

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MikeP090797 earned 680 total points
ID: 1441659
You can create your type of message and send it to a vb window. Then, in VB, using AdressOf and peek the message and proccess it.
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Author Comment

by:crl
ID: 1441660
TO MikeP:
I really need more detail for this answer to be helpful.
By creating my type of msg, do you mean something like
#define MY_MSG WM_USER + 100?
How exactly do I peek the msg?  Call PeekMessage frequently?
Can I pass a string as lparam from c++ with the msg and read it in vb?
thanks,
 
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Expert Comment

by:MikeP090797
ID: 1441661
By creating a new message I do mean a new number fro that message. You can pass any argument via lParam and wParam. To catch the message from VB, do the following:
In Globals:
Dim m_proc as long

In  Form_Load:
m_Proc = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf WindowProc)

Function WindowProc(hwnd as long, uMsg as long, wParam as long, lParam as long) as long

'Proccess your message.
'If lParam is a pointer to a string, use MoveMemory to retrive it. wParam must be the size of that string
Dim Buf as string *256
MoveMemory(lParam, Buf, wParam)

WindowProc = CallWindowProc(m_Proc, hwnd, uMsg, wParam, lParam)
End function

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Author Comment

by:crl
ID: 1441662
MikeP - thanks, I am trapping the message now, but I am still having problems copying the string that lparam points to.  Can you seethe problem with this code:

Public Declare Sub MoveMemory Lib "kernel32" Alias _ "RtlMoveMemory" (dest As Any, ByVal Source As Long, _
ByVal length As Long)

Function WindowProc(ByVal hw As Long, _
                    ByVal uMsg As Long, _
                    ByVal wParam As Long, _
                    ByVal lParam As Long) As Long
   
    If uMsg = UM_ACCOUNT_SELECTED Then
        Dim Buf As String * 256
        MoveMemory Buf, lParam, wParam
        MsgBox "ACCOUNT # = " & Buf
    Else
        WindowProc = CallWindowProc(lpPrevWndProc, hw, _
                                   uMsg, wParam, lParam)    
    End If
End Function

I see that I am passing wparam as the length of the lparam string correctly and that the address(lparam) is being passed correctly.  The MoveMemory statement is having no effect.  In fact I am having trouble using MoveMemory for local data in the vb project.

thanks for any help that you can give me.

Chris
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LVL 8

Expert Comment

by:MikeP090797
ID: 1441663
Try this declare:
Declare Sub MoveMemory Lib "kernel32" Alias "RtlMoveMemory" (ByRef hpvDest As Any, ByVal hpvSource As Any, ByVal cbCopy As Long)
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Author Comment

by:crl
ID: 1441664
I couldn't get MoveMemory to work.  I bought a good book "Hardcore Visual Basic" which has helped me by giving good explanations and samples.  I have filemapping working as shared memory.  Everything is looking good now.

Thanks MikeP
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