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======================================================================== MICROSOFT FOUNDATION CLASS LIBRARY : IPCWorkshop ======================================================================== AppWizard has created this IPCWorkshop application for you. This application not only demonstrates the basics of using the Microsoft Foundation classes but is also a starting point for writing your application. This file contains a summary of what you will find in each of the files that make up your IPCWorkshop application. IPCWorkshop.dsp This file (the project file) contains information at the project level and is used to build a single project or subproject. Other users can share the project (.dsp) file, but they should export the makefiles locally. IPCWorkshop.h This is the main header file for the application. It includes other project specific headers (including Resource.h) and declares the CIPCWorkshopApp application class. IPCWorkshop.cpp This is the main application source file that contains the application class CIPCWorkshopApp. IPCWorkshop.rc This is a listing of all of the Microsoft Windows resources that the program uses. It includes the icons, bitmaps, and cursors that are stored in the RES subdirectory. This file can be directly edited in Microsoft Visual C++. IPCWorkshop.clw This file contains information used by ClassWizard to edit existing classes or add new classes. ClassWizard also uses this file to store information needed to create and edit message maps and dialog data maps and to create prototype member functions. res\IPCWorkshop.ico This is an icon file, which is used as the application's icon. This icon is included by the main resource file IPCWorkshop.rc. res\IPCWorkshop.rc2 This file contains resources that are not edited by Microsoft Visual C++. You should place all resources not editable by the resource editor in this file. ///////////////////////////////////////////////////////////////////////////// AppWizard creates one dialog class: IPCWorkshopDlg.h, IPCWorkshopDlg.cpp - the dialog These files contain your CIPCWorkshopDlg class. This class defines the behavior of your application's main dialog. The dialog's template is in IPCWorkshop.rc, which can be edited in Microsoft Visual C++. ///////////////////////////////////////////////////////////////////////////// Other standard files: StdAfx.h, StdAfx.cpp These files are used to build a precompiled header (PCH) file named IPCWorkshop.pch and a precompiled types file named StdAfx.obj. Resource.h This is the standard header file, which defines new resource IDs. Microsoft Visual C++ reads and updates this file. ///////////////////////////////////////////////////////////////////////////// Other notes: AppWizard uses "TODO:" to indicate parts of the source code you should add to or customize. If your application uses MFC in a shared DLL, and your application is in a language other than the operating system's current language, you will need to copy the corresponding localized resources MFC42XXX.DLL from the Microsoft Visual C++ CD-ROM onto the system or system32 directory, and rename it to be MFCLOC.DLL. ("XXX" stands for the language abbreviation. For example, MFC42DEU.DLL contains resources translated to German.) If you don't do this, some of the UI elements of your application will remain in the language of the operating system. ///////////////////////////////////////////////////////////////////////////// ======================================================================== INTRODUCTION ======================================================================== The main objective of this application is to describe how simple the various Inter Process Communication methods can be used for data transfer. This application also help us to decide which of the available IPC methods are best to use.Inorder to explain the IPC methods effectively and simply, I have taken a structure pointer for description. The structure named EmployeeData is created and its pointer is passed from the client to the server. This demo application describes one way inter process communication (ie) from the client to the server for simplicity. The server will just listen to its clients. Here I have described 5 types of IPCs.( though Sockets are not said to be an IPC, it satisfies the data transfer purpose). 1 Clipboard Local Mc 2 File Mapping Local Mc 3 Named Pipes Local Mc/Intranet 4 Mailslots Local Mc/Intranet 5 Sockets Local Mc/Intranet/Internet ======================================================================== CLIPBOARD ======================================================================== The clipboard is a set of functions and messages that enable applications to transfer data. Because all applications have access to the clipboard, data can be easily transferred between applications or within an application. Procedure To Write in the Clipboard 1. OpenClipboard 2. Register Clipboard Format (Optional) 3. Use global allocation for the data 4. SetClipboardData 5. CloseClipboard. To Read from the Clipbaord 1. OpenClipboard 2. Register Clipboard Format (Optional) 3. Check the clipboard format is available 4. Get the clipboard data 5. Unlock the handle Clipboard format registration is Optional. Standard clipboard formats are available. Since Clipboard is used to transfer data in the local machine only, the server can be notified by posting message using HWND_BROADCAST. ======================================================================== FILE MAPPING ======================================================================== File mapping is an efficient way for two or more processes on the same computer to share data. Here i have not described about the synchronization of the process. In order to access the file's contents, the processes uses virtual address space called file view. Processes read from and write to the file view using pointers, just as they would with dynamically allocated memory. Procedure To write in the file 1. Create File Mapping 2. map the handle to the process virtual address space (MapViewOfFile) 3. copy the data in the file To Read from the File 1. Create File Mapping 2. MapViewOfFile (maps the handle to the process virtual address space) 3. copy the data from the file. Notify the server using HWND_BROADCAST handle. we have successfully trasferred the pointer between two processes on the same local machine. we will get curious of how to pass this pointer in the Intranet if this two processes resides on different computers. Next section is Named Pipes and Mailslots. ======================================================================== MAILSLOTS ======================================================================== Any win32 application can store messages in a mailslot and the owner will retrieve messages that are stored there. Mailslot is a simple way for a process to broadcast messages to multiple processes using datagram. Hence there won't be any confirmation of the receipt. This is a mechanism for one way inter process communication. Procedure To write in the Mailslot 1. CreateMailslot (Creates Mailslot) 2. WriteFile (write it to the mailslot) To Read from the Mailslot 1. CreateFile (opens the mailslot) 2. GetMailslotInfo (check for the messages in the mail slot) 3. Read from the Mailslot (ReadFile) A mailslot server is a process that creates and owns a mailslot. When the server creates a mailslot named MAILSLOT_EMPDATA it receives a mailslot handle. m_strMailslot = "\\\\.\\mailslot\\MAILSLOT_EMPDATA"; m_hInputslot