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Q135237: Windows 95 Hangs at Hourglass Starting SNA Server Win 3.x App

Article: Q135237
Product(s): Microsoft SNA Server
Version(s): WINDOWS:2.0,2.1,2.11,3.0,4.0
Operating System(s): 
Keyword(s): kbinterop kbnetwork sna4
Last Modified: 12-JUN-2001

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The information in this article applies to:

- Microsoft SNA Server, versions 2.0, 2.1, 2.11, 3.0, 4.0 
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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:
  1. Click the Start button, point to Settings, and click Control Panel. The
     Control Panel folder opens.

  2. Double-click Network. The Network dialog box appears.

  3. Select IPX/SPX-Compatible Protocol Properties, then choose the Properties
     button. The IPX/SPX-Compatible Protocol Properties dialog box appears.

  4. 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:
  1. Click the Start button, then click on Run. The Run dialog box appears.

  2. Type "regedit" and choose OK. Registry Editor starts.

  3. Open (click on the + next to) HKEY_LOCAL_MACHINE, then open System,
     CurrentControlSet, Services, and then finally open VxD.

  4. Select VNETSUP.

  5. From the Edit menu, select New, then choose String Value. A new value
     appears in the right pane.

  6. If necessary, right click on the new item and choose Rename from the
     context menu. Type DirectHost and press ENTER.

  7. Right click on DirectHost and choose Modify. The Edit String dialog
     appears.

  8. Type 0 (zero) and choose OK.

  9. Click on Registry then Exit to end the Registry Editor.

  This change will take effect when you next start Windows 95

  -or-

- 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-

- 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.

Additional query words: prodsna Win95 directhost hang

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Keywords          : kbinterop kbnetwork sna4 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ200 kbSNAServ211 kbSNAServ400 kbSNAServ210
Version           : WINDOWS:2.0,2.1,2.11,3.0,4.0

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