CServerMailslot & CClientMailslot v1.24 C++ wrapper classes for Win32 Mailslots

These 2 classes provides a clean C++ interface to the Win32 IPC mechanism called mailslots. They are very similar to the more common "Named pipe" IPC mechanism. Unlike named pipes, mailslots use datagrams. A datagram is a small packet of information that the network sends along the wire. Like a radio or television broadcast, a datagram offers no confirmation of receipt; there is no way to guarantee that a datagram has been received.

Mailslots can broadcast messages within a domain. If several processes in a domain each create a mailslot using the same name, every message that is addressed to that mailslot and sent to the domain is received by the participating processes. Because one process can control both a server and client mailslot handle, applications can easily implement a simple message-passing facility within a domain.

The enclosed zip file contains the source code for the 2 classes and also includes a VC 2017 solution to build a demonstration program called WinNotify. It is based on the old MS WinPopup utility as shown below:

Copyright

• You are allowed to include the source code in any product (commercial, shareware, freeware or otherwise) when your product is released in binary form.
• You are allowed to modify the source code in any way you want except you cannot modify the copyright details at the top of each module.
• If you want to distribute source code with your application, then you are only allowed to distribute versions released by the author. This is to maintain a single distribution point for the source code.

Updates

v1.24 (9 April 2022)

• Updated copyright details.
• Updated the code to use C++ uniform initialization for all variable declarations.

v1.23 (3 May 2020)

• Fixed more Clang-Tidy static code analysis warnings in the code.

v1.22 (26 December 2019)

• Fixed various Clang-Tidy static code analysis warnings in the code.
• Replaced BOOL with bool throughout the code.

v1.21 (21 September 2019)

• Fixed a number of compiler warnings when the code is compiled with VS 2019 Preview

v1.20 (3 June 2019)

• Updated copyright details
• Updated the code to clean compile on VC 2019

v1.19 (14 October 2018)

• Updated copyright details.
• Fixed a number of C++ core guidelines compiler warnings. These changes mean that the code will now only compile on VC 2017 or later.

v1.18 (30 April 2017)

• Updated copyright details.
• Updated the code to compile cleanly using /permissive-.

v1.17 (16 January 2016)

• Updated copyright details.
• Verified the code compiles cleanly in VC 2015

v1.16 (10 May 2015)

• Updated copyright details.
• Updated the project settings to more modern defaults
• Removed all unnecessary TRACE calls
• Made the classes into a header only implementation
• Updated the code to clean compile on VC 2013
• Reworked the CServerMailslot::Open and CClientMailslot::Open to provide the full mailslot name as its first parameter. This allows the class to avoid the use of CString
• Addition of a CServerMailslot::GetInfo method which encapsulates GetMailslotInfo.
• Removed the CServerMailslot::MessageWaiting, MessageCount, SizeOfWaitingMessage, MaximumMessageSize, GetCreationTime, GetLastAccessTime & GetLastWriteTime methods
• Added SAL annotations to all the code
• Reworked the CServerMailslot::Read method to use a pointer for returning the number of bytes read
• Reworked the CClientMailslot::Write method to use a pointer for returning the number of bytes write
• Replaced all ASSERT calls with ATLASSERT. This means that the class can now be used without the need to pull in MFC

v1.15 (7 September 2008)

• Updated copyright details.
• Code now compiles cleanly using Code Analysis (/analyze)
• Updated code to compile correctly using _ATL_CSTRING_EXPLICIT_CONSTRUCTORS define
• Updated sample app to clean compile on VC 2008
• The code has now been updated to support VC 2005 or later only.
• Removed VC 6 style AppWizard comments from the code.
• Updated the sample app to improve on the error reporting.

v1.14 (8 September 2007)

• Updated copyright details.
• Minor code tidy up.

v1.13 (23 December 2006)

• Code now uses CString instead of raw TCHAR buffers in various functions
• Classes now do not derive from CObject as it was not really required

v1.12 (22 December 2006)

• Updated copyright details
• Updated the documentation to use the same style as the web site
• Optimized CServerMailslot constructor code
• Addition of a CMAILSLOT_EXT_CLASS preprocessor macro to allow the classes to be more easily added to an extension dll
• Reviewed all TRACE statements for correctness
• Optimized CClientMailslot constructor code
• Updated the code to clean compile on VC 2005
• Code now uses newer C++ style casts instead of C style casts.
• Changed the default size of the formview window in the sample ap to avoid scroll bars using default fonts.

v1.11 (26 July 2003)

• Updated copyright details.
• Fixed issue in CClientMailslot::Open which was causing it to only allow one instance of the mailslot to be opened. Thanks to GdP Software for reporting this problem.

11 August 1998

• Inclusion of a VC 5 make file.
• Tidy up of the resources the program uses plus their names.

v1.11 (10 August 1998)

• Fixed a bug in the Close function of both classes where the mailslot handle was not being set back to INVALID_HANDLE_VALUE.

v1.1 (26 July 1998)

• Provision of Unicode build configurations
• Fixed a bug in CClientMailslot destructor
• CServerMailslot::Close() & CClientMailslot::Close() now work correctly when the mailslot is already closed
• Fixed a level 4 warning in the CWinNotifyDoc in the demo program.
• Complete documentation for the classes is now provided in the form of a HTML file
• Changed 2 functions which used a pointer parameter to now use a C++ reference instead.