SAMPLE: WNBDemo.exe Uses NetBIOS Under Microsoft Windows

ID: Q84071

The information in this article applies to:

Microsoft Windows Device Development Kit (DDK) for Windows, versions 3.0, 3.1

SUMMARY

WNBDemo.exe is a sample that contains sample source code and additional documentation for NetBIOS under Windows. In the Microsoft Windows operating system, an application can use NetBIOS functions in every Windows mode (real, standard, or 386 enhanced). However, the application must conform to some rules, which are briefly discussed in the text below.

MORE INFORMATION

The following file is available for download from the Microsoft Download Center. Click the file name below to download the file:

WNBDemo.exe

For more information about how to download files from the Microsoft Download Center, please visit the Download Center at the following Web address

http://www.microsoft.com/downloads/search.asp

and then click How to use the Microsoft Download Center.

NOTE: Microsoft C Optimizing Compiler version 6.0 or later and Microsoft Macro Assembler (MASM) version 5.1 or later are required to build the source code in WNBDEMO.

Windows provides access to NetBIOS through the NetBIOSCall function. This function is equivalent to issuing Interrupt 5Ch under MS-DOS. Although it is legal to call Interrupt 5Ch directly from within Windows, this is not the recommended practice; use NetBIOSCall.

An application should call the NetBIOSCall() function from assembly language to ensure that the registers are preserved for the call. The following is a short stub function that can be used to issue NetBIOS calls under Windows:


    extrn     NETBIOSCALL : FAR
   extrn     DOS3CALL : FAR
   
             assume  cs: _TEXT
   
   _TEXT     SEGMENT WORD PUBLIC 'CODE'
   
   
   ; WORD FAR PASCAL nbNetBIOS(LPNCB lpNCB)
   
             PUBLIC  nbNetBIOS
   
   nbNetBIOS proc FAR
   
             push    bp                    ; save bp
             mov     bp, sp                ; sp into bp for stack access
             push    es                    ; save es
             push    bx                    ; save bx
   
             mov     es, word ptr [bp + 8] ; put HIWORD into es
             mov     bx, word ptr [bp + 6] ; put LOWORD into bx
   
             call    NetBIOSCall           ; shazam!
   
             xor     ah, ah
             mov     al, byte ptr es:[bx + 1] ; return the return code
   
             pop     bx                    ; restore bx
             pop     es                    ; restore es
             mov     sp, bp                ; restore sp
             pop     bp                    ; restore bp
             ret     4                     ; return to caller
                                           ; fix-up stack
   
   nbNetBIOS endp
   
   
   _TEXT     ENDS
   
   END

This function takes a FAR pointer to an initialized network control block (NCB) and returns the NCB's return code from the NetBIOS driver.

Unlike MS-DOS, Windows also has special memory requirements for NCBs and post routines. The general rule of thumb is to fix the NCBs and post routines in memory as much as possible to prevent paging, banking, or other time-consuming operations during the time that the application uses the NCBs and post routines.

For post routines, all code and data segments used by the routine must be placed into FIXED segments of a dynamic-link library (DLL). This causes the segments to be page locked, not banked, and to have other attributes appropriate to the mode in which Windows is running. Because the FIXED keyword is ignored for applications, this code must be placed in a DLL.

Remember that the post routine may call only the PostMessage(), PostAppMessage(), and NetBIOSCall() functions; it cannot call any other functions in Windows. To call the nbNetBIOS function given above from the post routine, nbNetBIOS must be placed into a FIXED segment of a DLL and the function must be reentrant.

NCBs should be allocated such that they are also page locked, not banked, and have other attributes appropriate to the mode in which Windows is running. The easiest way to do this is to use GlobalAlloc() to allocate memory for the NCB either as GMEM_FIXED or to call the GlobalWire() function to move the memory as low as possible in the address space (followed by a call to GlobalPageLock() in 386 enhanced mode). If the memory is allocated from a DLL with the GMEM_FIXED flag, then the memory will also be page locked--this is true only for allocations from DLLs.

As stated above, for further information, refer to the WNBDEMO.exe in the Microsoft Software Library.

REFERENCES

"An Introduction to Network Programming Using the NetBIOS Interface," by Alok Sinha and Ray Patch, March-April 1992 Microsoft Systems Journal

Additional query words:

Keywords : kbfile kbnetwork kbsample kbGrpNet kbNETBOIS
Version : :3.0,3.1
Platform :
Issue type :