INFO: Interprocess Communication Under Windows NT, 95, & Win32s

ID: Q95900

The information in this article applies to:

SUMMARY

The following are some of the standard mechanisms available for interprocess communication (IPC): NetBIOS, mailslots, windows sockets (winsock), named pipes, anonymous pipes, semaphores, shared memory, and shared files. Other IPC mechanisms available on Microsoft systems include DDE, OLE, memory-mapped files, Windows messages, Windows atoms, the registration database, and the clipboard.

MORE INFORMATION

The table below denotes what platforms and subsystems provide which IPC mechanisms (this does not imply that all the mechanisms will interoperate between different subsystems):

Interprocess Communication Mechanisms

   IPC Mechanism  WinNT  Win95  Win32s(1)  Win16(2)  MS-DOS(2)  POSIX  OS/2
   -------------  -----  -----  ---------  --------  ---------  -----  ----

             DDE  YES    YES    YES        YES        NO         NO     NO
         OLE 1.0  YES    YES    YES        YES        NO         NO     NO
         OLE 2.0  YES    YES    YES        YES        NO         NO     NO
         NetBIOS  YES    YES    YES        YES       YES         NO    YES
     Named pipes  YES    YES(3) YES(3)     YES(3)    YES(3)     YES(4) YES
 Windows sockets  YES(5) YES    YES        YES(5)     NO         NO(6)  NO
       Mailslots  YES    YES    YES(3)      NO        NO         NO    YES
      Semaphores  YES    YES     NO         NO        NO        YES    YES
             RPC  YES    YES(7) YES(8)     YES       YES         NO     NO
 Mem-Mapped File  YES    YES    YES         NO        NO         NO     NO
     WM_COPYDATA  YES    YES    YES(9)     YES        NO         NO     NO
NOTES:

(1) Win32s an extension to Windows 3.1, which allows Win32-based 

    applications to run under Windows 3.1. Win32s supports all the Win32
    APIs, but only a subset provides functionality under Windows 3.1. Those
    APIs that are not functional return ERROR_CALL_NOT_IMPLEMENTED.
(2) This is technically not a subsystem.

(3) Cannot be created on Win16, Windows 95 and MS-DOS workstations, but can 

    be opened.
(4) The POSIX subsystem supports FIFO queues, which do not interoperate 
    with Microsoft's implementation of named pipes.
(5) Through the Windows sockets API.

(6) Currently BSD-style sockets are under consideration for the POSIX 

    subsystem.
(7) Windows 95 supports the RPC 1 protocol only. The NetBios protocol is 
    not supported. Namedpipe servers are not supported.
(8) Win32s version 1.1 provides network support through Universal Thunks.

(9) Under Win32s, WM_COPYDATA does not actually copy the data -- it 

    only translates the pointers to the data. If the receiving application
    changes the buffer, then the data is changed for both applications.
(10) OLE objects created in a Win32 service must be in the same user 
   context as a logged on user that wishes to use them.  Any attempt to
   access these objects from a different user context will result in
   failure.  For example, a service that runs under the LocalSystem account
   creates an object that an application running in Domain\User's context
   attempts to access will fail.
Additional query words: Keywords : kbnetwork kbAPI kbIPC kbKernBase kbNTOS310 kbNTOS350 kbNTOS351 kbNTOS400 kbSDKPlatform kbWinOS95 kbWinsock kbGrpNet

Last Reviewed: September 10, 1998