RE: socket api question - is it possible for recv() to receive 0bytefrom server?

Thanks Scott.  That clears it up.  I was not sure if recvLen will be 0
or -1 when alarm() signal occurred.  

Not sure if it is good practice, I've always check for recvLen < 0 as
indication for error.  In you example, you specifically check for -1.



-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Scott Klement
Sent: Friday, November 17, 2006 9:14 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: socket api question - is it possible for recv() to receive
0bytefrom server?


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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