Creating a Mailslot

Mailslots are supported by three specialized functions: CreateMailslot, GetMailslotInfo, and SetMailslotInfo. These functions are used by the mailslot server.

The following code sample uses the CreateMailslot function to retrieve the handle to a mailslot named "sample_mailslot". The code sample in Writing to a Mailslot shows how client application can write to this mailslot.

#include <windows.h>
#include <stdio.h>

HANDLE hSlot;
LPCTSTR SlotName = TEXT("\\\\.\\mailslot\\sample_mailslot");

BOOL WINAPI MakeSlot(LPCTSTR lpszSlotName) 
{ 
    hSlot = CreateMailslot(lpszSlotName, 
        0,                             // no maximum message size 
        MAILSLOT_WAIT_FOREVER,         // no time-out for operations 
        (LPSECURITY_ATTRIBUTES) NULL); // default security
 
    if (hSlot == INVALID_HANDLE_VALUE) 
    { 
        printf("CreateMailslot failed with %d\n", GetLastError());
        return FALSE; 
    } 
    else printf("Mailslot created successfully.\n"); 
    return TRUE; 
}

void main()
{ 
   MakeSlot(SlotName);
}

To create a mailslot that can be inherited by child processes, an application should change the SECURITY_ATTRIBUTES structure passed as the last parameter of CreateMailslot. To do this, the application sets the bInheritHandle member of this structure to TRUE (the default setting is FALSE).