sdk/samples/all in on code/Visual Studio 2008/CppMailslotClient/CppMailslotClient.cpp

   1 /****************************** Module Header ******************************\
   2 Module Name:  CppMailslotClient.cpp
   3 Project:      CppMailslotClient
   4 Copyright (c) Microsoft Corporation.
   5
   6 Mailslot is a mechanism for one-way inter-process communication in the local
   7 machine or across the computers in the intranet. Any clients can store
   8 messages in a mailslot. The creator of the slot, i.e. the server, retrieves
   9 the messages that are stored there:
  10
  11 Client (GENERIC_WRITE) ---> Server (GENERIC_READ)
  12
  13 This sample demonstrates a mailslot client that connects and writes to the
  14 mailslot "\\.\mailslot\SampleMailslot".
  15
  16 This source is subject to the Microsoft Public License.
  17 See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.
  18 All other rights reserved.
  19
  20 THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
  21 EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
  22 WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
  23 \***************************************************************************/
  24
  25 #pragma region Includes
  26 #include <stdio.h>
  27 #include <windows.h>
  28 #include <assert.h>
  29 #pragma endregion
  30
  31
  32 void WriteMailslot(HANDLE hMailslot, PCWSTR pszMessage);
  33
  34
  35 int wmain(int argc, wchar_t *argv[])
  36 {
  37     // The name of the mailslot. It is in the form of \\.\mailslot\[path]name
  38     // The name field must be unique. The name may include multiple levels of
  39     // pseudo directories separated by backslashes. For example, both
  40     // \\.\mailslot\mailslot_name and \\.\mailslot\abc\def\ghi are valid.
  41     const PCWSTR MAILSLOT_NAME = L"\\\\.\\mailslot\\SampleMailslot";
  42
  43     HANDLE hMailslot = INVALID_HANDLE_VALUE;
  44     DWORD dwError = ERROR_SUCCESS;
  45
  46     // Open the mailslot with write access (Mailslot is a mechanism for one-
  47     // way IPC. The client is just responsible for writing to the mailslot.)
  48     hMailslot = CreateFile(
  49         MAILSLOT_NAME,              // The name of the mailslot
  50         GENERIC_WRITE,              // Write access
  51         FILE_SHARE_READ,            // Share mode
  52         NULL,                       // Default security attributes
  53         OPEN_EXISTING,              // Opens existing mailslot
  54         FILE_ATTRIBUTE_NORMAL,      // The file has no other attributes set
  55         NULL                        // No template file
  56         );
  57     if (hMailslot == INVALID_HANDLE_VALUE)
  58     {
  59         dwError = GetLastError();
  60         wprintf(L"Unable to open mailslot w/err 0x%08lx\n", dwError);
  61         goto Cleanup;
  62     }
  63
  64     wprintf(L"The mailslot (%s) is opened.\n", MAILSLOT_NAME);
  65
  66     // Write messages to the mailslot.
  67
  68     WriteMailslot(hMailslot, L"Message 1 for mailslot");
  69     WriteMailslot(hMailslot, L"Message 2 for mailslot");
  70     Sleep(3000); // Sleep for 3 seconds for the demo purpose
  71     WriteMailslot(hMailslot, L"Message 3 for mailslot");
  72
  73 Cleanup:
  74
  75     // Centralized cleanup for all allocated resources.
  76     if (hMailslot != INVALID_HANDLE_VALUE)
  77     {
  78         CloseHandle(hMailslot);
  79         hMailslot = INVALID_HANDLE_VALUE;
  80     }
  81
  82     return dwError;
  83 }
  84
  85
  86 //
  87 //   FUNCTION: WriteMailslot(HANDLE, PCWSTR);
  88 //
  89 //   PURPOSE: Write a message to the specified mailslot.
  90 //
  91 //   PARAMETERS:
  92 //      * hMailslot - The handle of the mailslot.
  93 //      * pszMessage - The message to be written to the slot.
  94 //
  95 void WriteMailslot(HANDLE hMailslot, PCWSTR pszMessage)
  96 {
  97     assert(hMailslot != INVALID_HANDLE_VALUE);
  98     assert(pszMessage != NULL);
  99
 100     DWORD cbMessageBytes = 0;       // Message size in bytes
 101     DWORD cbBytesWritten = 0;       // Number of bytes written to the slot
 102
 103     // Calculate the message size (including the NULL terminator) in bytes.
 104     cbMessageBytes = (wcslen(pszMessage) + 1) * sizeof(*pszMessage);
 105
 106     BOOL fSucceeded = WriteFile(    // Write to the mailslot.
 107         hMailslot,                  // Handle of the slot
 108         pszMessage,                 // Message to be written
 109         cbMessageBytes,             // Number of bytes to write
 110         &cbBytesWritten,            // Number of bytes written
 111         NULL                        // Not overlapped
 112         );
 113
 114     if (!fSucceeded || cbMessageBytes != cbBytesWritten)
 115     {
 116         wprintf(L"WriteFile failed w/err 0x%08lx\n", GetLastError());
 117     }
 118     else
 119     {
 120         wprintf(L"The message \"%s\" is written to the slot\n", pszMessage);
 121     }
 122 }