Using Mailslots

Listing 1: msserver.cpp
Mail Slot Server

// msserver.cpp

#include <tchar.h>
#include <windows.h>
#include "msserver.h"
#include "msname.h"

BOOL CALLBACK ServerDlgProc(HWND, UINT, WPARAM, LPARAM);
HINSTANCE hInst;
HANDLE hMailSlot; 

//---------------------------------------------------------------
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInst,
                     LPSTR lpCmdLine, int nCmdShow)
{
    // The mailslot server creates the mailslot that will be used
    // by the mailslot clients and reads messages from it.

    TCHAR szSlotName[MAX_PATH];
    lstrcpy(szSlotName, TEXT("\\\\.\\mailslot\\"));
    lstrcat(szSlotName, MY_MAILSLOT_NAME);

    hMailSlot = CreateMailslot(szSlotName, // mailslot name
                               0,          // max message size
                               5000,       // wait 5 sec for msg
                               (LPSECURITY_ATTRIBUTES)NULL);
 
    if (hMailSlot == INVALID_HANDLE_VALUE) {
        return FALSE;
    } 

    // Create the dialog box to display mailslot information.

    hInst = hInstance;
    DialogBox(hInst, MAKEINTRESOURCE(SERVER_DLG), NULL, 
              ServerDlgProc);

    // Close the mailslot handle.

    CloseHandle(hMailSlot);
    return 0;

} // WinMain

//---------------------------------------------------------------
int CALLBACK ServerDlgProc(HWND hDlg, UINT Message,WPARAM wParam,
                         LPARAM lParam)
{
    TCHAR szMsg[1024];

    switch (Message) {
        case WM_INITDIALOG:
            return TRUE;

        case WM_COMMAND:
            switch (LOWORD(wParam)) {
            case ID_GETINFO: {
                    
                // Display current mailslot info.

                DWORD dwMaxMsgSize = 0, dwNextMsgSize = 0,
                      dwMsgCount = 0, dwReadTimeout = 0;

                if (GetMailslotInfo(hMailSlot,
                                    &dwMaxMsgSize,
                                    &dwNextMsgSize,
                                    &dwMsgCount,
                                    &dwReadTimeout)) { 

                    SetDlgItemInt(hDlg, ID_MAXMSGSIZE, 
                                  dwMaxMsgSize, TRUE);
                    SetDlgItemInt(hDlg, ID_NEXTMSGSIZE, 
                                  dwNextMsgSize, TRUE);
                    SetDlgItemInt(hDlg, ID_READTIMEOUT, 
                                  dwReadTimeout, TRUE);
                    SetDlgItemInt(hDlg, ID_MSGCOUNT, 
                                  dwMsgCount, TRUE);
                }
                break;
            }

            case ID_READ:
                    
                // Read and display message from mailslot.

                DWORD dwBytesRead = 0;

                if (ReadFile(hMailSlot, (LPBYTE)szMsg, 1024,
                             &dwBytesRead, NULL)) {
                    SetDlgItemText(hDlg, ID_MESSAGE, szMsg);
                } else {
                    wsprintf(szMsg, 
                             TEXT("ReadFile failed (%d)"),
                             GetLastError());
                    SetDlgItemText(hDlg, ID_MESSAGE, szMsg);
                }
            }
            break;

        case WM_CLOSE:
            EndDialog(hDlg, 1);
            break;

        default:
            return FALSE;
    }
    return FALSE;

} // ServerDlgProc