Q113190: Npclnt.exe WFW Named Pipe Client

Article: Q113190
Product(s): Windows for Workgroups and Windows NT Networking Issues
Version(s): 3.11
Operating System(s): 
Keyword(s): kbfile kbnetwork kbsample kbAPI kbIPC kbPipes kbSDKPlatform kbOSWin311 kbGrpDSNet
Last Modified: 13-JUN-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) for Windows for Workgroups, version 3.11 
-------------------------------------------------------------------------------

SUMMARY
=======

The sample Npclnt.exe in the Microsoft Download Center demonstrates the named
pipe client interface in Windows for Workgroups (WFW).

This sample provides a WFW named pipe client for the Win32 SDK named pipe sample
(NPSERVER). This sample opens, reads, and writes to the named pipe created by
the NPSERVER application. The DosReadAsyncNmPipe API is used to perform
asynchronous reads from the server's named pipe to avoid blocking under WFW.

NOTE: This sample has two problems.

- The NP callback should be in a fixed code segment in a DLL.

- Memory passed to DosReadAsyncNmPipe and DosWriteAsyncNmPipe should be fixed
  and pagelocked.

MORE INFORMATION
================

The following file is available for download from the Microsoft Download
Center:

  DownloadDownload Npclnt.exe now

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. Once posted, the file is housed on secure
servers that prevent any unauthorized changes to the file.


Care must be taken when using DosReadAsyncNmPipe or DosWriteAsyncNmPipe. Because
both APIs provide WFW a function pointer that is called at interrupt time, only
limited operations may be performed in the callback. The WFW SDK reference
states the following about the callback function:

  Generally, the callback function can set global variables and check the
  variable specified by the pusErrCode parameter for potential errors. But the
  callback function must not modify registers or call any MS-DOS system
  functions, BIOS functions, or C run-time functions that call MS- DOS and BIOS
  functions. Although the callback function can call the PostMessage function,
  it must not call the SendMessage function.

Also, the callback function must be exported in the application's *.DEF file.
Besides exporting, the application must call MakeProcInstance on the function
before calling the asynchronous API. Care must also be taken not to call
FreeProcInstance while a read or write is outstanding.

Additional query words: WFW Workgroups Named Pipe DosReadAsyncNmPipe DosWriteAsyncNmPipe

======================================================================
Keywords          : kbfile kbnetwork kbsample kbAPI kbIPC kbPipes kbSDKPlatform kbOSWin311 kbGrpDSNet 
Technology        : kbAudDeveloper kbSDKSearch kbWinSDKSearch kbWinSDK311
Version           : :3.11
Issue type        : kbinfo

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.