INF: How to Determine if DBNMPIPE.EXE Is Loaded from C Program

• Microsoft SQL Server Programmer's Toolkit, version 4.2

SUMMARY

This article discusses how a DB-Library (DB-Lib) application can determine whether the DBNMPIPE.EXE TSR is loaded.

MORE INFORMATION

The following program uses Interrupt 21h Function 35H to find the address of the current interrupt handler for Interrupt 62h, where the DBNMPIPE.EXE terminate-and-stay-resident (TSR) program installs itself. It then compares 9 bytes from that address, after an initial offset of 2 bytes, to "DBLIBRARY". If the TSR program is loaded, these bytes will match.

#include <dos.h>
#include <memory.h>
#include <stdio.h>

void main(void) {
    union REGS inregs, outregs;
    struct SREGS segregs;
    int result;
    char *ptr;

    inregs.h.ah = 0x35;
    inregs.h.al = 0x62;
    result = int86x(0x21,&inregs,&outregs,&segregs);
    FP_OFF(ptr) = outregs.x.bx + 2;
    FP_SEG(ptr) = segregs.es;
    result = memcmp((char *)ptr,"DBLIBRARY",9);
    if (result == 0)
        printf("\nDBNMPIPE is loaded\n");
    else
        printf("\nDBNMPIPE is not loaded\n");
}