VB Forum / COM / September 2007

I am attempting to write a demo C app that will send custom data to a VB
app. I am using SendMessageTimeout, and WM_COPY.

This is the C structure that I am sending from the C code:

typedef struct
{
    GUID        guid ;
    UnsignedInt    version ;
    SourceType    srcId ;
    EventType    eventId ;
    char         msg[MSG_MAX_MSG_LEN+1] ;
} ConsoleMsgStruct ;

I am able to receive the message in my VB6 WindowProc callback. However,
the problem is retreiving the fields from the received message.

Here are the types I am using in VB:

Private Type GUID
  Data1 As Long         '4 bytes
  Data2 As Long         '4 bytes
  Data3 As Long         '4 bytes
  Data4(8) As Byte      '8 bytes
End Type

Private Type ConsoleMsg
    the_guid    As GUID         '20 bytes
    version     As Integer      '2 bytes
    srcId       As Integer      '2 bytes
    eventId     As Integer      '2 bytes
    msg         As String * 128 '128 bytes
End Type

Private Type COPYDATASTRUCT
    dwData As Long
    cbData As Long
    lpData As Long
End Type

This is my VB callback (WindowProc)

Public Function ListenerWindowProcCallback(ByVal hwnd As Long, _
                              ByVal wMsg As Long, ByVal wParam As Long, _
                              ByVal lParam As Long) As Long

    Dim recvd       As ConsoleMsg
    Dim cdata       As COPYDATASTRUCT
    Dim pBytes      As Long

    If wMsg = WM_COPYDATA Then
        Debug.Print "Custom msg received. wParam is: " & wParam

    //Note: I am not sure if these are necessary or being used correctly
here ...
        CopyMemory cdata, lParam, Len(cdata)
        pBytes = VarPtr(cdata.lpData)

    'FIXME: This does not seem to work. The data I get is corrupted
        CopyMemory recvd, pBytes, 152

    Else
        '\\Pass the message to the previous
        ListenerWindowProcCallback = CallWindowProc(hOldProc, hwnd,
wMsg, wParam, lParam)
    End If

End Function

Does anyone Know how I may fix the above code, so that the variable
recvd is correctly populated?