Re: Gethostbyaddr

[Scott Klement <klemscot@xxxxxxxxxxxx>]

Sigh...   I've already answered this message wrong twice, because my brain
fell out and rolled away.

Anyway... this has nothing to do with WinXP or Win2k. Neither
gethostbyname() or gethostbyaddr() actually contacts the computer
that you're looking up, so it doesn't matter what their operating
systems are.

All it does it ask the DNS server.  The DNS server will have a file
called a "zone file" which contains a list of computers and their
addresses.

To do reverse lookup, it reverses the IP address and makes a hostname
that it can check for. If the IP address is "1.2.3.4", then it will look
for "4.3.2.1.IN-ADDR.ARPA" in your zone file.

Make sure you have your PCs defined in that matter, and you should be all
set.



On Wed, 18 Jun 2003, Jonathan Giles wrote:
>
> I have an RPG program I copied from Midrange (thank you Scott Klement )
> using the gethostbyaddr API and it worked well on my W2k machines.  I
> have upgraded my machines to XP and the program no longer returns the
> host name.  I have the latest patches applied (06/18/2003).
>
> Jon Giles
>
> hdebug dftactgrp( *no ) bnddir( 'QC2LE' )
> Dinet_addr        PR            10U 0 ExtProc('inet_addr')
> D  IPAddr                         *   Value options(*string)
>
> DGetHostByAddr    PR              *   ExtProc('gethostbyaddr')
> D  HostEnt                      10U 0
> D  AddrLen                      10I 0 Value
> D  AddrType                     10I 0 Value
>
> DHostEntP         S               *
>
> Dhostent          DS                   Based(HostEntP)
> D  h_name                         *
> D  h_aliases                      *
> D  h_addrtype                    5I 0
> D  h_length                      5I 0
> D  h_addr_list                    *
>
> DIP32Addr         S             10U 0
> DAF_INET          C                   Const(2)
> C     *Entry        PList
> C                   Parm                    P#IPAddress      15
> C                   Parm                    P#IPName         64
>
>  * Convert IP to binary format:
> C                   Eval      IP32Addr  =  inet_addr(P#IPAddress)
>
>  * do reverse DNS lookup:
>
> C                   Eval      HostEntP = gethostbyaddr(IP32Addr :
> C                                                     %size(IP32Addr) :
> C                                                     AF_INET)
>
>  * set results
>
> C                   if        HostEntP  = *Null
> C                   Eval      P#IPName  = 'Host not found!'
> C                   Else
> C                   Eval      P#IPName  = %str(h_name)
> C                   endif
> C                   SetOn                                        Lr
> C                   Return