FILE: Developing Network Applications for Windows 3.1

• Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1

SUMMARY

This article is part of a set of seven articles, collectively called the "Windows Developer's Notes" that are available in NETWORK.EXE. More information about the contents of the other articles can be found in the Microsoft Knowledge Base article:

Q65260 The Windows Developer's Notes

MORE INFORMATION

The following file is available for download from the Microsoft Software Library:

Network.exe

Q119591 How to Obtain Microsoft Support Files from Online Services

• Applications should be well behaved when shared by multiple users.



• Applications that access network software directly might require special measures to be compatible with protected (standard or 386 enhanced) mode.

=======================================================================
                   BEING SHARED BY MULTIPLE USERS
=======================================================================

Many corporations are choosing to have their computer users share a single
copy of an application that resides on a network server. Microsoft Windows
version 3.1 can be run this way. The Windows Setup /n (network) option
configures the user's system, which ensures that most Windows files are
used directly off the network, while the user's personal files and
configuration information are stored in a private Windows directory. (See
the "Microsoft Windows User's Guide" for more information on using a shared
copy of Windows.)

If the developer intends to allow shared copies of an application, then the
developer must make sure that two users running the same application will
not interfere with each other. The following sections present rules that
should help the developer design the application for network support.

CREATING PERMANENT FILES
========================

Many applications store configuration files in the same directory as the
application's own executable file. This method will not work for multiple
users because the application will store each user's information in the
same directory, overwriting other users' information.

Instead, the application should use the GetWindowsDirectory() function to
find the user's private Windows directory. This location is guaranteed to
be unique for each user.

Refer to the "Microsoft Windows Software Development Kit Reference"
for more information on the GetWindowsDirectory() function.

CREATING TEMPORARY FILES
========================

When creating temporary files, use the GetTempFilename() function to
determine the name and location of the file. This function will ensure that
temporary filenames will not conflict, even if multiple users are sharing
the same temporary storage directory.

USING PROFILE STRINGS
=====================

Profile and configuration information is usually stored in initialization
(.INI) files using Windows functions such as WriteProfileString(). These
functions fall into two categories: those that access WIN.INI, and those
that access another .INI file specified by the program.

The following functions access WIN.INI:

 - GetProfileString()
 - GetProfileInt()
 - WriteProfileString()

Because each user has a unique copy of WIN.INI, these functions can be used
safely, even when the application is being shared by more than one user.

The following functions access other initialization files:

 - GetPrivateProfileString()
 - GetPrivateProfileInt()
 - WritePrivateProfileString()

These functions behave similarly to the WIN.INI functions, except that the
application specifies the name of the private initialization file. When
using these functions, the developer should specify the name of the file;
however, a complete pathname should not be used (for example, MYAPP.INI
should be used instead of C:\MYAPP\MYAPP.INI.) By default, the file will be
located in the user's private Windows directory; specifying a full pathname
could give multiple users access to the same file.

Initialization files that need to be shared among all users are the
exception to this rule. Make sure that such files cannot be left in an
inconsistent state if multiple users update them simultaneously.

For a full description of the initialization file functions, see the
Windows SDK (Software Development Kit) reference manual.


=======================================================================
             CALLING NETWORK SOFTWARE IN PROTECTED MODE
=======================================================================

Windows-based applications running in protected mode require special
support whenever they make a function call to real-mode software. This
includes calls to MS-DOS, the BIOS, or a network. However, applications
that are not based on Windows but are running with Windows do not require
this special support because they always run in real or virtual-8086 mode.

The main support required is called "API mapping." If the arguments to the
call include pointers to data, that data should be copied down into the
first 1 MB of address space to ensure that the real-mode software can
access it. The processor is then switched into real or virtual-8086 mode to
ensure that the real-mode software can process the call. Finally, when that
call returns, any data it modified is copied back up to the caller's
protected-mode address.

Fortunately, most applications interact with the network only indirectly,
by using MS-DOS functions to manipulate files on redirected drive letters,
or by using MS-DOS or BIOS calls to print to a remote printer using
redirected printer ports. Windows-based applications can continue to
perform these functions normally because Windows automatically maps
standard MS-DOS and BIOS calls.

However, some applications need to use functions that are specific to a
particular network or networking protocol. Some part of the software must
map these APIs, and in some cases this may require special procedures on
the part of the programmer.

The remainder of this document describes programming considerations for
designing Windows-based applications that use the following networking
protocols and networks:

 - Microsoft Networks and MS-DOS network functions
 - NetBIOS functions
 - Microsoft LAN Manager-based networks
 - Novell NetWare
 - Ungermann-Bass Net/One
 - Banyan VINES


MICROSOFT NETWORKS AND MS-DOS NETWORK FUNCTIONS
===============================================

Many networks on the market today are based on the Microsoft Network
standard, also known as MS-NET. These networks support a set of standard MS-
DOS functions that perform network activities, such as redirecting drive
letters.

Windows automatically handles these MS-DOS functions. However, to maintain
compatibility with future Windows products, the application should not make
MS-DOS calls by executing an INT 21H instruction. Instead, it should set up
all the registers for executing the INT 21H and then make a far call to the
Windows DOS3Call() function.

See the Windows SDK reference manual for a full description of the
DOS3Call() function. See the "MS-DOS Encyclopedia," available from
Microsoft Press, for more information on Microsoft Network functions.

NETBIOS FUNCTIONS
=================

NetBIOS is the most widely used networking API. These functions are
normally called using INT 5CH. Windows handles most NetBIOS functions.
However, to maintain compatibility with future Windows products, the
application should not make the NetBIOS call by executing an INT 5CH
instruction. Instead, it should set up all the registers for executing the
INT 5CH, and then make a far call to the Windows NetBIOSCall() function.

The following rarely-used NetBIOS functions are not supported:

   Function  Description
   --------  -----------

   71H       Send.No.Ack
   72H       Chain.Send.No.Ack
   73H       Lan.Status.Alert
   78H       Find.Name
   79H       Trace

See the Windows SDK reference manual for a full description of the
NetBIOSCall() function. See the "IBM Local Area Network Technical
Reference" for more information on NetBIOS.

LAN MANAGER-BASED NETWORKS
==========================

Networks based on Microsoft LAN Manager can be installed in either Basic or
Enhanced versions.

All versions of LAN Manager support MS-NET and NetBIOS functions. However,
if LAN Manager Enhanced is being used with the API option, applications can
also use a powerful set of networking functions.

Applications that are not based on Windows can call these functions by
linking with DOSNET.LIB, a static library provided with the network
software. However, Windows-based applications must use DLLs (Dynamic-Link
Libraries) called NETAPI.DLL and PMSPL.DLL, which are distributed on every
LAN Manager version 2.x Enhanced workstation. Note that these DLLs will not
run on LAN Manager version 1.x or 2.x Basic; therefore, these functions may
only be used on LAN Manager version 2.x Enhanced.

See the "Microsoft LAN Manager Programmer's Reference" for more details on
writing Windows-based applications for LAN Manager.

NOVELL NETWARE
==============

Novell NetWare supports MS-NET and, optionally, NetBIOS functions, which
are described earlier in this document.

In addition, Novell NetWare also supports the NetWare and IPX/SPX API sets,
all based on INT 21H.

Windows-based applications can make NetWare calls; however, this cannot be
done by executing the INT 21H directly because this method is not supported
in all Windows operating modes. Instead, the INT 21H instruction should be
replaced with a far call to the NetWareRequest() function. This function is
exported by name from the NetWare DLL, and should be imported to the module-
definition (.DEF) file as NetWare.NetWareRequest.

UNGERMANN-BASS NET/ONE
======================

Ungermann-Bass Net/One is based upon the Microsoft Network standard. It
supports standard MS-NET and most NetBIOS functions, which are described
earlier in this document.

Net/One also supports private extensions to the NetBIOS function set
(functions 72H-7DH). These functions are supported by the standard
Windows product. These functions can be called as standard NetBIOS
functions would be called, by making a far call to the NetBIOSCall
function.

BANYAN VINES
============

Banyan VINES supports the standard MS-NET and, optionally, NetBIOS
functions. There is also a toolkit for applications that write directly to
the VINES API.

Windows-based applications can call the MS-NET and NetBIOS functions as
previously described. 

Additional query words:

Keywords : kbfile kbnetwork kbAPI kbSDKPlatform kbWinOS310 kbWinOS300 kbGrpNet
Version : WINDOWS:3.0,3.1
Platform : WINDOWS
Issue type :