Solved

I'm having trouble with the CreateMailslot function.

Posted on 1997-05-16
2
555 Views
Last Modified: 2006-11-17
I've been trying to use the CreateMailslot function from kernel32 and I keep getting an INVALID_HANDLE_VALUE returned by the call.

I've tried the following C++ code in a DLL and it works :-

#include <iostream.h>
#include <windows.h>

long create_slot (void);

HANDLE hM_slot;


BOOL WINAPI DllEntryPoint (HINSTANCE hDll, DWORD dwReason, LPVOID Reserved)

{
      switch (dwReason)
      {
            case DLL_PROCESS_ATTACH:
            {
                  break;
            }
            case DLL_PROCESS_DETACH:
            {
                  break;
            }
      }
      return TRUE;
}

long create_slot (void)
{
      hM_slot=CreateMailslot("\\\\.\\mailslot\\test_mail_slot",0,MAILSLOT_WAIT_FOREVER,(LPSECURITY_ATTRIBUTES) NULL);
      return hM_slot;
}

In VB 4.0 I tried the following :-

Type SECURITY_ATTRIBUTES
        nLength As Long
        lpSecurityDescriptor As Long
        bInheritHandle As Boolean
End Type

Declare Function CreateMailslot Lib "kernel32" Alias "CreateMailslotA" (ByVal lpName As String, ByVal nMaxMessageSize As Long, ByVal lReadTimeout As Long, lpSecurityAttributes As SECURITY_ATTRIBUTES) As Long

Global slot_num As Long
Global Const MAILSLOT_WAIT_FOREVER = (-1)


Private Sub Command1_Click()
    Dim security As SECURITY_ATTRIBUTES
    slot_num = CreateMailslot("\\.\mailslot\mailslottest", 0, MAILSLOT_WAIT_FOREVER, security)
    MsgBox slot_num
End Sub

It doesn't work! So I tried this :-

Declare Function CreateMailslot Lib "kernel32" Alias "CreateMailslotA" (ByVal lpName As String, ByVal nMaxMessageSize As Long, ByVal lReadTimeout As Long, lpSecurityAttributes As Any) As Long

Global slot_num As Long
Global Const MAILSLOT_WAIT_FOREVER = (-1)


Private Sub Command1_Click()
    slot_num = CreateMailslot("\\.\mailslot\mailslottest", 0, MAILSLOT_WAIT_FOREVER, Null)
    MsgBox slot_num
End Sub

Still doesn't work!
0
Comment
Question by:mikekr
2 Comments
 
LVL 5

Accepted Solution

by:
y96andha earned 100 total points
ID: 1426348
It has to do with the specification of the C value NULL. Use this code:

Private Declare Function CreateMailslot Lib "kernel32" Alias "CreateMailslotA" (ByVal lpName As String, ByVal nMaxMessageSize As Long, ByVal lReadTimeout As Long, ByVal lpSecurityAttributes As Long) As Long
Private slot_num As Long
Private Const MAILSLOT_WAIT_FOREVER = (-1)

Private Sub Command1_Click()
slot_num = CreateMailslot("\\.\mailslot\mailslottest", 0, MAILSLOT_WAIT_FOREVER, 0)
MsgBox slot_num
End Sub



0
 

Author Comment

by:mikekr
ID: 1426349
Thanks... It worked!!!!
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
vb6 programatically bring window to front 8 63
Microsoft Access combo box help 2 37
Convert VB6 MSXML2.ServerXMLHTTP process to C# 2 41
Help me. 3 45
The debugging module of the VB 6 IDE can be accessed by way of the Debug menu item. That menu item can normally be found in the IDE's main menu line as shown in this picture.   There is also a companion Debug Toolbar that looks like the followin…
If you need to start windows update installation remotely or as a scheduled task you will find this very helpful.
As developers, we are not limited to the functions provided by the VBA language. In addition, we can call the functions that are part of the Windows operating system. These functions are part of the Windows API (Application Programming Interface). U…
Get people started with the process of using Access VBA to control Outlook using automation, Microsoft Access can control other applications. An example is the ability to programmatically talk to Microsoft Outlook. Using automation, an Access applic…

911 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

20 Experts available now in Live!

Get 1:1 Help Now