Re: SOCKET Connect() connects but shouldn't.

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Hi Dave,

The code you posted got cut off because it was too long.  Since you don't 
use the RdLine() routine, and you use WrLine() only once and it's not 
realted to the problem, I just omitted that code.  I added the /DEFINE 
ERRNO_LOAD_PROCEDURE and /COPY ERRNO_H to the bottom of the code and 
compiled it on my system.

However, when I run your code, the connect() API returns -1 and the 
program ends, just as expected.

I'm at V5R3.  I'm behind on PTFs by, oh, probably 6 months. My iSeries 
does not use satellite (it uses a fractional T1) but I don't see why 
that'd matter.

I agree that trying a different Internet connection might help debug 
things. Or maybe just take a PC into the office during off hours and 
connect it directly to the iSeries (with a hub/switch in between or with a 
crossover cable) and do the tests straight from the iSeries to the PC with 
nothing in the middle.

Heck, just trying it with another computer on the LAN would probably be 
adequate.

- - -

There are a bunch of things I didn't like in your code (I'm a little 
picky) I'll tell you what they are so you can decide whether you'd like to 
take my advice and change them:

> From your code sample:

     D addrCvtr        PR            10U 0 extproc('inet_addr')
     D                               15A   options(*varsize) const

This is wrong.  The inet_addr() API requires a null-terminated string, but 
this prototype doesn't do that.  The code will work 99% of the time 
because most of the unallocated memory on the iSeries is filled with null 
characters...  but, you don't want your code to fail 1% of the time with 
weird errors that are difficult to debug :)

The prototype SHOULD look like the following one:

     D addrCvtr        PR            10U 0 extproc('inet_addr')
     D                                 *   value options(*string)

Note that you already have the correct prototype for inet_addr in your 
source member with the above definition, but it's called inet_addr() 
rather than renaming it to addrCvtr().  IMHO, it's a bad idea to rename it 
like this.

Why should you call it "inet_addr" instead of "addrCvtr"?  To be kind to 
me (or people like me) when I read your code. :)

When someone sees "addrCvtr" in your code, what will they do?  Since 
that's a name of your devising, it won't be familiar to them, and they'll 
have to search around to find it. Maybe they'll search the Information 
Center (as I did) and find no hits.  Maybe they'll search the web and find 
nothing.  Eventually they'll find in your code where you renamed 
inet_addr() to addrCvtr() but why put them through that?

All of the documentation refers to the API as inet_addr(). It's called 
inet_addr not only on the iSeries, but on Unix, Windows, etc, etc. It's a 
standard API used all over the place.  It's just easier to follow your 
code when you don't rename it like that.

Another thing that doesn't make sense, but isn't causing a problem:

    C                   Eval      I_Net_Adr   = %trim(I_Net_Adr)

What was this code intended to do?  I_Net_Adr is a fixed-length 20A field. 
When you do RtvNetAds(device) it assigns an IP address to this field. So 
prior to the above %trim() statement it'll look something like this:

'192.168.100.100     '

The %trim() BIF will remove those 5 blanks from the right-hand side of the 
string, making it 15 chars long.  Since it's only 15 chars long, the EVAL 
operation will add 5 blanks to the end in order to make it fit in a 20A 
field?  The result is that you just stripped off the 5 blanks and added 
them back, creating a little bit of work for the computer, but 
accomplishing nothing.

You can just omit that line of code, since it doesn't do anything. 
(Granted, it doesn't hurt anything, either, but why do it?)

There's a similar problem later in your code:

     C                   Eval      bufOut = *Blanks
     C                   Eval      bufOut = %Trimr(bufOut) +
     C                                      'MYDATAGOESHERE'

This is what that code does:

a) Take the BufOut field, which contains 32k worth of blanks, and replace 
all 32767 blanks with new blanks.  (Taking some CPU time, but 
accomplishing nothing.)

b) Use the %trimr() BIF to remove those 32767 blanks that you just added.

c) Put 'MYDATAGOESHERE' at the start of the string, and then add 32753 
blanks on to the end.

You can solve the problem by simply coding:

     C                   Eval      bufOut = 'MYDATAGOESHERE'

You also appear to have most (if not all) of the code from my SOCKET_H 
member included directly in your program.  In my opinion, that makes the 
code more difficult to read because it makes the source member 
significantly longer, and therefore is more stuff for the next programmer 
to take in.

Just use /COPY to bring in the definitions (like you did for ERRNO_H and 
SOCKUTIL_H)

Not only that, but putting them in a separate source member makes the next 
socket related program easier to write since you don't have to copy the 
code from member to member.  You can just use the same /copy statement in 
the new program

You also have multiple ways to retrieve "errno" in the code. You have 
mine, and you have $$Errno. I'd recommend picking one and using that 
method exclusively... it's confusing to have two of them.

You also have prototypes for the read() and write() with comments saying 
that you'll use them to read and write from the socket.  If you want to 
use those APIs, you can, they'll work just fine.  but I recommend putting 
them in a /copy member, and then not using send() and recv() in the code. 
There's no reason to use both, and having them both in your program's 
definitions is confusing.

And you have unlink(). Were you planning to delete files from the IFS?  I 
didn't see any mention of it in the code you posted.  Again, the fact that 
it's there just adds to the confusion... if you don't need it, why's it 
there?

Sorry for being long-winded, and I hope my words above are helpful.

---
Scott Klement  http://www.scottklement.com



On Sun, 5 Feb 2006, Dave Johnson wrote:

> Scott, thank you for helping me try to understand this.  I've posted the 
> program code on midrange.com here: 
> http://code.midrange.com/index.php?id=86383b016d
>
> That's my entire program. I realize it's full of a lot of extraneous 
> procedures that are not even used here, but I just copied your copy 
> books in so I wouldn't miss anything.  The shotgun approach.
>
> I changed the socket(xxxx call to use literals instead of the constants, 
> even though I'm sure the constants were fine. BUt just to be sure you 
> know.
>
> If it makes any difference at all... I am connected to my iseries over a 
> two-way satellite using a satellite modem.  I don't know why that would 
> matter but maybe direcway does some weird stuff there.
>
> I wish I had a dial up account somewhere so I could test this that way 
> and see if I get the same results. That'd tell me for sure that's its 
> something on my modem or network or connection that's causing the 
> problem if the dial up worked.
>
> Thanks,
>
> Dave Johnson