Using Mailslots

Listing 5: msclient.cpp
Mail Slot Client

// msclient.cpp

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

BOOL CALLBACK ClientDlgProc(HWND, UINT, WPARAM, LPARAM);
HINSTANCE hInst;

//---------------------------------------------------------------
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInst,
                     LPSTR lpCmdLine, int nCmdShow)
{
    // This client opens the mailslot and writes messages to it.

    hInst = hInstance;
    DialogBox(hInst, MAKEINTRESOURCE(CLIENT_DLG), NULL, 
              ClientDlgProc);

    return 0;

} // WinMain

//---------------------------------------------------------------
int CALLBACK ClientDlgProc(HWND hDlg, UINT Message,WPARAM wParam,
                           LPARAM lParam)
{
    switch (Message) {
        case WM_INITDIALOG:
            CheckRadioButton(hDlg,ID_LOCAL,ID_PRIMARY,
                             ID_LOCAL);
            return TRUE;

        case WM_COMMAND:
            switch (LOWORD(wParam)) {
            case ID_WRITE: {

                TCHAR szSlotName[1024], sz[1024];
                DWORD dwMaxMsgSize = 0, dwNextMsgSize = 0, 
                      dwMsgCount = 0, dwReadTimeout = 0;
                    
                // Form name of mailslot

                if(IsDlgButtonChecked(hDlg,ID_LOCAL)) {
                    // mailslot on local computer
                    lstrcpy(sz, TEXT("."));
                } else if(IsDlgButtonChecked(hDlg,ID_REMOTE)) {
                    // mailslot on remote computer
                    GetDlgItemText(hDlg,ID_COMPUTERNAME,sz,64);
                } else if (IsDlgButtonChecked(hDlg,ID_DOMAIN)){
                    // all computers on the domain
                    GetDlgItemText(hDlg,ID_DOMAIN,sz,64);
                } else {
                    // all computers on the primary domain
                    lstrcpy(sz, TEXT("*"));
                }
    
                wsprintf(szSlotName,
                         TEXT("\\\\%s\\mailslot\\%s"), 
                         sz, MY_MAILSLOT_NAME);

                // Open the mailslot

                HANDLE hMailSlot; 
                hMailSlot = CreateFile(szSlotName, 
                                       GENERIC_WRITE, 
                                       FILE_SHARE_READ,
                                       NULL, OPEN_EXISTING,
                                       FILE_ATTRIBUTE_NORMAL, 
                                       NULL);
                if (hMailSlot != INVALID_HANDLE_VALUE) {
                        
                    // Write message to mailslot
                        
                    DWORD dwBytes, dwBytesWritten;

                    GetDlgItemText(hDlg, ID_MESSAGE,sz, 1024);
                    dwBytes = (lstrlen(sz)+1) * sizeof(TCHAR);
                    WriteFile(hMailSlot, (LPBYTE)sz, dwBytes, 
                              &dwBytesWritten, NULL);

                    // Close the mailslot handle.

                    CloseHandle(hMailSlot);
                }
                break;
            }
            }
            break;

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

        default:
            return FALSE;
    }
    return FALSE;

} // ClientDlgProc