RE: Programmatically Pull the IP Address of The iSeries

[Scott Klement <midrange-l@xxxxxxxxxxxxxxxx>]

Terry,

> RTVNETA    SYSNAME(&SYSNAME)

This is the SNA/APPC system name.


> PING       RMTSYS(&SYSNAME)
> RCVMSG     MSGTYPE(*INFO) MSG(&MSGDTA)
> CHGVAR     VAR(&IPADDR) VALUE(%SST(&MSGDTA 57 12))

This is the TCP/IP DNS name.  Nothing requires this to match the SNA name. 
Granted, many people would probably use the same name for both SNA and 
DNS, but there's no promise that this'll always work.  Heck, you could 
actually end up pinging a different system this way!

Also, there's nothing that forces the IP address to always be in position 
57 of the message.  Anyone could use CHGMSGD to change the position. IBM 
could re-word the text of the message in the next release of OS/400. You 
could install a different language on the system, and it'd be in a 
different position.  You should be getting the address from the message 
data, rather than from the message itself!

Worse, you've hard-coded the length at 12. If the IP address were 
"207.100.123.206' your program would try to ping '207.100.123.' chopping 
off the last number.  If the IP address were '9.3.21.4' your program would 
grab the whole address plus part of the wording that comes after it.


> CHGVAR     VAR(&PATH) VALUE('net use T: \\' *TCAT +
>             &IPADDR *TCAT '\CMTEMP')

This is Windows Networking.  Only in newer versions of Windows can you use 
the IP address in a UNC name, in older versions you have to use the 
NetBIOS name.

And, naturally, the NetBIOS name is not the same as the SNA name or DNS 
name.  Granted, the admin might make them all the same for consistency, 
but he doesn't have to...  just like the DNS name.

Furthermore, the whole idea of getting the IP address for a "machine" is 
flawed. IP addresses are assigned to network interfaces, they're not 
assigned to computers.

You'd be better off hard-coding the name, or putting it in a data area 
that's easily changed, than you would writing code like the one you posted 
here.  That way, it's simple and won't mislead the next guy.

If you REALLY want to write program that figures it out yourself, you need 
to use the correct APIs.  gethostname() will tell you the host name of 
your system.  gethostbyname() will perform a DNS or host table lookup on 
a domain name to get it's IP address.  The QZLSLSTI API can be used to get 
the Windows Networking name of the server.