Re: Question on socket non block read

Scott,
Going back to the article, I see where you initially set the socket to non
blocked.
When I attempt to implement this logic, I receive an error with the fcntl
function:
Flags = FCntl(Sock
: F_GetFL);
Flags = %BitOr(Flags : O_NONBLOCK);
FCntl(Sock
: F_SETFL
RNF7416: The types of the right and left hand side do not match in the EVAL
operation.
: Flags);

My prototype is:
D fcntl PR 10I 0 ExtProc('fcntl')
D SocketDesc 10I 0 Value
D Command 10I 0 Value
D Arg 10I 0 Value Options(*NOPASS)

The definition for F_GETFL is:
D F_GETFL C CONST(6)

V6R1M0.

Any idea why this is causing a problem?

TIA.


Jeff Young
Sr. Programmer Analyst

On Sun, Sep 20, 2015 at 1:20 AM, Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>
wrote:

Jeff,

Yes, I understand all of that.

The reason it works when you have data in the socket is because the recv()
API will return the data instead of waiting for more.

A blocking socket will sit and wait for more data. A non-blocking socket
never sits and waits for more data.

This is NOT done within the nbrecv() routine... it must be done by you
before you call nbrecv. The article explains how to put the socket into
non-blocking mode. If you haven't put it into nonblocking mode. You will
have the problem that you are reporting.

I understand what you are saying about moving the select before the recv
-- personally, i think this is a poor solution. In my experience, your
application will be more robust with the recv() first and using a
non-blocking socket.

-SK

On 9/18/2015 1:09 PM, Jeff Young wrote:

Scott,
I was using the nbrecv procedure from the article
http://iprodeveloper.com/rpg-programming/timeouts-sockets.
I copied the code from there and was using that version.
As long as the socket contained data, there was no problem.
As soon as there was no data available, the recv() function just hung up.
I changed my procedure to move the recv() after the select() and now it is
working fine.

--
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