The document provides an overview of various Inter-Process Communication (IPC) mechanisms in the Windows operating system, including clipboard, data copy, Dynamic Data Exchange (DDE), Component Object Model (COM), file mapping, mailslots, pipes, Remote Procedure Call (RPC), and sockets. Each mechanism is described along with the relevant Windows API functions used for communication between applications, highlighting their unique features and methods of data exchange. The document serves as a concise reference for understanding how different IPC methods function in Windows environments.

1. IPC mechanisms in Windows
A brief description of different IPC
mechanisms in Windows OS
Compiled By:
B. Vinoth Raj
Senior Software Engineer
Mindfire Solutions

2. IPC mechanisms in Windows
 Clipboard
 Data Copy
 Dynamic Data Exchange (DDE)
 Component Object Model (COM)
 File Mapping
 Mailslots
 Pipes
 Remote Procedure Call (RPC)
 Sockets

3. IPC using Clipboard
 Loosely coupled exchange medium
 Applications agree on data format
 Following Windows API functions used
OpenClipboard()
EmptyClipboard()
SetClipboardData()
CloseClipboard()
GetClipboardData()
 Applications can reside on the same computer or on
different computers on a network

4. IPC using Data Copy
 Use WM_COPYDATA windows message to share data
 SendMessage() API function used to send data
 COPYDATASTRUCT structure used to send data
SendMessage(hwnd, // Handle to destination window
WM_COPYDATA, // Message to send to destination window
(WPARAM)wparam, // Handle to window passing the data
(LPARAM)lparam); // Data (pointer to COPYDATASTRUCT)
 The data sent is read-only for the receiving application
 Works only for processes running on same computer

5. IPC using DDE
 DDE is a message-based protocol
 Uses shared memory to exchange data
 Share data between applications running on the same
computer or on different computers on a network
 Nine DDE message are defined. All DDE transactions are
conducted by passing these messages b/w client and
server
 An application calls SendMessage to issue the
WM_DDE_INITIATE message or a WM_DDE_ACK
message sent in response to WM_DDE_INITIATE

6. IPC using DDE (cont.)
 All other messages are sent by PostMessage
LRESULT WINAPI SendMessage( _In_ HWND hWnd,
_In_ UINT Msg,
_In_ WPARAM wParam,
_In_ LPARAM lParam);
 First parameter of these calls is a handle to the receiving
window
 Second parameter contains the message to be sent
 Third parameter identifies the sending window
 Fourth parameter contains the message-specific
arguments

7. IPC using File Mapping
 Allows one-way and bi-directional communication between
applications
 Windows API functions used: CreateFileMapping(),
MapViewOfFile(), UnMapViewOfFile(), CloseHandle()
 A synchronization object (e.g., semaphore) is required to
prevent data corruption in multi-tasking environment
 Uses shared memory for data sharing

8. IPC using File Mapping (cont.)
 Server process does the following:
– Create file mapping by invoking CreateFileMapping function
– Map the view of the file mapping into the address space of the current process
(MapViewOfFile)
– Use CopyMemory function to write message to the file view
– Unmap the file view and close the file mapping objects (UnmapViewOfFile,
CloseHandle)

9. IPC using File Mapping (cont.)
 Client process does the following:
– Open a named file mapping using OpenFileMapping
– Map the view of the file mapping into the address space of the current process
using MapViewOfFile
– Read message from the view of the shared memory
– Unmap the file view and close the file mapping objects (UnmapViewOfFile,
CloseHandle)

10. IPC using Mailslots
 Provides one-way communication
 Process that creates mailslot is a mailslot server
 Mailslot clients send data to mailslot server
 Mailslot IPC mechanism is a Windows only feature
 A process can be both mailslot server and mailslot client so
two-way communication is possible using multiple
mailslots
 Mailslot messages can be broadcasted

11. IPC using Mailslots (cont.)
 A mailslot server does the following:
- Create a mailslot using CreateMailslot() function
- Check messages in the mailslotusing ReadMailslot() function
- Check for the number of messages in the mailslotusing GetMailslotInfo() function
- Retrieve the messages one by one from the mailslot. While reading, update the number of
messages that are left in the mailslot. (ReadFile, GetMailslotInfo)
- Close the handle of the mailslot instance using CloseHandle() function

12. IPC using Mailslots (cont.)
 A mailslot client does the following:
- Open the mailslot using CreateFile() function
- Write messages to the mailslot. (WriteMailslot, WriteFile)
- Close the slotusing CloseHandle() function

13. IPC using Pipes
 Allows two-way communication
 Two types of pipes available: named and anonymous
 Named pipes are used to transfer data between unrelated
processes
 Anonymous pipe works between processes on same
computer
 To have two-way communication, two anonymous pipes
can be used

14. IPC using Pipes (cont.)
 Windows API functions used are:
CreateNamedPipe()
ConnectNamedPipe()
WaitNamedPipe()
DisconnectNamedPipe()
ReadFile()
WriteFile()
CloseHandle()
 A Named Pipe name needs to be in the following format:
For named pipe server – .pipePipeName
For named pipe client – ComputerNamepipePipeName

15. IPC using Windows sockets
 Socket is a communication endpoint
 Applications can send or receive packets of data across a
network
 Two types of sockets available
Stream Sockets – stream of bytes. No record boundaries
Datagram Sockets - record-oriented data flow that is not guaranteed to be delivered
Packets may not be sequenced and duplication can occur

16. IPC using Sockets (cont.)
 Sockets are highly useful in at least three communications
contexts:
– Client/Server models
– Peer-to-peer scenarios, such as chat applications
– Making remote procedure calls (RPC) by having the
receiving application interpret a message as a function call

17. Thanks!