RE: socket api question - is it possible for recv() to receive 0byte from server? -- RPG400-L

Scott

As you say, functions that set errno do not change it if they endsuccessfully. That is why it is good practice in C to set it to 0before any call to such a function. I have been able to set errno inRPG - just need to call the geterrno() function (I think) to retrieveit the first time, so that the pointer is set to the location oferrno. After that, the variable based on the pointer to errno can beset to 0. Least it has worked for me - i've tried to learn my lessonsabout 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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