Npclnt.exe WFW Named Pipe Client (113190)

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:

Download Npclnt.exe now

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

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to 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.