Microsoft KB Archive/135237

= Windows 95 Hangs at Hourglass Starting SNA Server Win 3.x App =

Article ID: 135237

Article Last Modified on 3/23/2004

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APPLIES TO


 * Microsoft SNA Server 2.0
 * Microsoft SNA Server 2.1
 * Microsoft SNA Server 3.0
 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0

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This article was previously published under Q135237



SUMMARY
The SNA Server Windows 3.x client software is supported on Windows 95. However, if the SNA Server client software is configured to use the "Microsoft Networking (named pipes)" interface and Windows 95 is configured with Microsoft IPX/SPX-compatible protocol (the default), starting an SNA Server Windows 3.x client application will cause Windows 95 to hang with an hourglass.

At that point, you must enter CTRL+ALT+DEL to bring up the Windows 95 Close Program dialog, highlight the task named "SNA Server (Not responding)", choose "End Task", and confirm the selection by choosing "End Task" again.

This causes the Windows 95 hourglass to disappear and the SNA Server Windows 3.x client process, WNAP.EXE, is stopped After that, the SNA Server Windows 3.x application can be stopped using the "End Task" option.



CAUSE
When the SNA Server Windows 3.x client software is configured to use the named pipes interface, the SNA Server client software always posts a DosReadAsyncNmPipe API call on the named pipe. This causes a Read request to always be posted to the server. While the Read request is outstanding, the SNA client software also may write data down the named pipe as well, so the SNA client makes use of the full-duplex nature of the named pipe API, supported over any LAN protocol provided by Windows 95 (that is, NetBEUI, IPX/SPX, TCP/IP, RAS, etc).

However, if the Microsoft IPX/SPX-compatible transport is installed and the "direct-host" feature is enabled on Windows 95, this network interface only allows a single command to be outstanding on the client-server LAN session (that is, this only provides a half-duplex communication channel to the server). So, the SNA Server client named pipe interface does not work properly.

To contrast, Windows 95 file and print redirection and SQL Server named pipe clients do work over "direct-host" IPX/SPX connections because only a single command is outstanding at a time (that is, the DosReadAsyncNmPipe call is not used).



WORKAROUND
Any of the following three workarounds can be used to resolve this problem:

 If you wish to keep the Microsoft IPX/SPX Compatible protocol installed, the IPX/SPX NetBIOS interface must be enabled and the directhost feature must be disabled (see below for instructions),

To enable the NWLINK NetBIOS interface:  Click the Start button, point to Settings, and click Control Panel. The Control Panel folder opens. Double-click Network. The Network dialog box appears. Select IPX/SPX-Compatible Protocol Properties, then choose the Properties button. The IPX/SPX-Compatible Protocol Properties dialog box appears. Choose (check) the I Want To Enable NetBIOS Over IPX/SPX check box. and choose OK.

This change will take effect when you next start Windows 95.

To disable the IPX/SPX DirectHost feature:  Click the Start button, then click on Run. The Run dialog box appears.</li> Type "regedit" and choose OK. Registry Editor starts.</li> Open (click on the + next to) HKEY_LOCAL_MACHINE, then open System, CurrentControlSet, Services, and then finally open VxD.</li> Select VNETSUP.</li> From the Edit menu, select New, then choose String Value. A new value appears in the right pane.</li> If necessary, right click on the new item and choose Rename from the context menu. Type DirectHost and press ENTER.</li> Right click on DirectHost and choose Modify. The Edit String dialog appears.</li> Type 0 (zero) and choose OK.</li> Click on Registry then Exit to end the Registry Editor.</li></ol>

This change will take effect when you next start Windows 95

-or-</li> Keep the SNA Server named pipes interface enabled, remove the Microsoft IPX/SPX-compatible transport and install a different Microsoft transport (such as NetBEUI or TCP/IP) using the Windows 95 network control panel.

-or-</li> Configure the SNA Server Windows 3.x client software to use an interface other than named pipes, by running the SNA Server client setup program installed in the SNA Server client program group.</li></ul>

Additional query words: prodsna Win95 directhost hang

Keywords: kbinterop kbnetwork KB135237

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