RE: socket api question - is it possible for recv() to receive0by te from server?

This is my errno function.
http://code.midrange.com/index.php?id=ff408987e1

It works exactly as errno in C. 
To initialaze errno, execute errNo(0) and when errno returns a non-zero
value execute an errno(0) again to clear the last error like the example
below:

errNo(0);

fd = Open(...

If errNo <> 0;
   // report error
   errNo(0);
EndIf;  

Duane Christen


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of Vernon Hamberg
Sent: Friday, November 17, 2006 10:59 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: socket api question - is it possible for recv() to
receive0byte from server?


Scott

As you say, functions that set errno do not change it if they end 
successfully. That is why it is good practice in C to set it to 0 
before any call to such a function. I have been able to set errno in 
RPG - just need to call the geterrno() function (I think) to retrieve 
it the first time, so that the pointer is set to the location of 
errno. After that, the variable based on the pointer to errno can be 
set to 0. Least it has worked for me - i've tried to learn my lessons 
about pointers from you!!


Vern

At 09:14 PM 11/17/2006, you wrote:

Errno may not be reset from a previous value.  For example, if you call
recv() once, and receive EINTR, errno will remain set to EINTR until some
other error occurs.

Therefore, you shouldn't use errno to detect if there's an error or not.
You should only check it's value when you know that there's an error, and
you want to know what the error is.

Personally, I typically do something like this:

         recvlen = recv( . . . );

         if (recvlen = -1);
             err = errno;
             select;
             when err = EINTR;
                 // timeout!
             when err = (other expected error);
                 // handle appropriately
             other;
                 errMsg = %str(strerror(Errno));
                 // show error to user;
             endsl;
         endif;

         // no error -- handle received data.

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

On Fri, 17 Nov 2006, Lim Hock-Chai wrote:

Cool!  Thanks.

One more question:
What is the proper way to check for alarm().
C                   eval      recvlen = recv(hostSock :%addr(recvData)
C                                           :%size(recvData)-10
C                                           :0)
 *       disable timeout
C                   callp     alarm(0)

 *       leave if timeout occur
C                   if        recvLen <= 0 and (errno = EINTR)
C                   leave
C                   endif


Should I even check the recvLen?
Should I replace
C                   if        recvLen <= 0 and (errno = EINTR)
with
C                   if        errno = EINTR

Thanks


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of David Gibbs
Sent: Friday, November 17, 2006 10:19 AM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: socket api question - is it possible for recv() to receive
0byte from server?

Lim Hock-Chai wrote:

I've a client socket program that is connecting to a non-AS400 system
using SOCK_STREAM connection type.

This RPG program uses alarm() to break the recv() block.  Every so
often, the program seems to be receiving 0 byte from the server before

the alarm is trigger.

Is it possible for recv() to receive 0 byte for server?

Take a look at
http://archive.midrange.com/midrange-l/199906/msg00487.html.

david
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