|
Determining a PC's IP Address
by Shannon O'Donnell
To communicate with a PC from an RPG IV program, an important piece of information
you'll need is the PC's IP. If you were only communicating with a single or a finite
number of PCs, and those PCs always had the same IP address each time they logged onto
your iSeries, you could store the IP address in a database file on your iSeries. That
way you could just retrieve the local workstation ID for the iSeries job and look it up
in the table of IP addresses, and you'd be all set. But that scenario is not likely
to happen.
Any time a PC logs onto your iSeries via the Internet, it's almost guaranteed to have a different IP address each time. This is
because IP addresses are limited in quantity, and are therefore valuable property. A
person's Internet service provider needs to recycle IP addresses each time a PC connects
to the Internet and then gets off again. This allows the ISP to reuse IP addresses, thereby
cutting down on the number of IP addresses an ISP needs to have for a given set of users.
And this same scenario is possible, and even likely, on a local area network where DHCP
is used to provide dynamic IP addresses to PCs as they log on and off the local area
network. The point is, you can't ever count on a PC having the same IP address every
time it logs onto your system. Therefore, you need a way to programmatically determine
the PC's IP address at runtime. With RPG IV and an iSeries API, accomplishing this goal
is easy.
The sample program below demonstrates how to use the QDCRDEVD (Retrieve Device Description)
API to retrieve a PC's IP address. The sample program shown here contains a prototype, a
couple of C-specs, and a subprocedure, to demonstrate how to obtain the IP address of the
PC running this sample.
Feel free to modify this code and play with it until you are comfortable with the way it
works. In this issue of Midrange Programmer, you'll find the first of a series of
articles from Ted Holt discussing prototypes and procedures. Since Ted will cover these
concepts in much more detail, I won't explain the how's and why's of using them here.
Rest assured, however, that you can copy and paste this code, as is, into any RPG IV
program, or run it as shown here--it will work fine either way. And while you're doing
that, we'll see what other handy little programs and procedures we can come up with to
make your life as a programmer easier!
*==========================================================
* To Compile:
*
* CRTBNDRPG PGM(XXX/RTVIPADR1)
*
* Function: Retrieve IP address of PC
*
*==========================================================
H DFTACTGRP(*NO) BNDDIR('QC2LE')
D RtvIpAdr PR 20a
D Device 10a CONST
*
D I_Net_Adr S 16a
*
D SDS
D Device 244 253
*---------------------------------------------------------
* Retrieve IP Address
C Eval I_Net_Adr = RtvIpAdr(Device)
C Eval I_Net_Adr = %trim(I_Net_Adr)
C I_Net_Adr Dsply
C Eval *Inlr = *On
*---------------------------------------------------------
* RtvIpAdr - Subprocedure To Retrieve PC's IP Address
*---------------------------------------------------------
P RtvIpAdr B Export
D RtvIpAdr PI 20A
D Inp_Device 10A Const
D Apierr DS
D Bytprv 1 4B 0 Inz(216)
D Bytavl 5 8B 0 Inz
D Errid 9 15A Inz
D Rsvd 16 16A Inz
D Errdta 17 216A Inz
D Net_Address S 20A INZ
D Format S 8A Inz('DEVD0600')
D Rcvar S 5000A Inz
D Varlen S 4B 0 Inz(5000)
C Eval Device = Inp_Device
C Call 'QDCRDEVD'
C Parm Rcvar
C Parm Varlen
C Parm Format
C Parm Device
C Parm Apierr
C If BytAvl = 0
C Eval Net_Address = %Subst(Rcvar:877:16)
C Endif
C Return Net_Address
P RtvIpAdr E
|
Sponsored
By
SOFTLANDING SYSTEMS |
|
Thinking HIGH AVAILABILITY?
Think SOFTWARE MANAGEMENT First!
80% of unplanned downtime is caused by Application Failure or
Operator Error, not hardware failure, according to IBM’s iSeries 400
Availability Team.
Software Management is essential to keeping your applications
available, reliable, and bug-free, no matter how often you update
them. Let SoftLanding show you how. You'll finish software projects
faster, with a higher degree of quality, and keep them online, using
our industry-leading solutions for CHANGE MANAGEMENT, DEBUGGING,
TESTING, DEPLOYMENT, DATABASE REORGS, and PROBLEM DIAGNOSIS &
RESOLUTION.
High Availability through Software Management. For more info and
FREE downloads, visit http://www.softlanding.com/products/400
or email info@softlanding.com.
|
|
