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Newsgroups: comp.lang.ada
Date: Wed, 25 Oct 2017 10:23:50 -0700 (PDT)
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Subject: alternative for buggy accept_socket to create a non-blocking version
From: Matt Borchers <mattborchers@gmail.com>
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Xref: news.eternal-september.org comp.lang.ada:48591
Date: 2017-10-25T10:23:50-07:00
List-Id: <comp.lang.ada>

I have no choice but to use an old GNAT compiler -- version 6.3.0.  In this=
 version there is a confirmed bug (fixed in 6.3.2) that prevents the non-bl=
ocking version of accept_socket from working.  I want to call the version o=
f accept_socket with the 'timeout' parameter, but it doesn't do what it sho=
uld.

Basically, I've built a way to read data from a socket and all goes well wh=
en a response is made.  However, I need a way to abandon the accept call if=
 a response is never sent within a small time window.

This is my foray into sockets programming and I don't fully understand all =
of the nuances yet.  I tried setting the Receive_Timeout socket option but =
it had no effect -- I don't think it does what I need anyway.  This all see=
ms pretty straight-forward assuming there is no bug in the non-blocking ver=
sion of accept_socket, but I don't know how to work-around this bug.

I can imagine a pair of tasks in which one does the blocking accept (A) and=
 the other task (B) does the time-out.  If the time-out occurs first, B wil=
l abort the task A otherwise after A succeeds in accepting the message it w=
ill abort B.  This seems like it might not be the best work-around solution=
.

Does anybody know of a good way to create a type of non-blocking accept_soc=
ket?

My code basically is:

with GNAT.Sockets; use GNAT.Sockets;
...
declare
  sock,
  socket   : SOCKET_TYPE;
  address  : SOCK_ADDR_TYPE;
  data     : STREAM_ELEMENT_ARRAY(1..256);
  last     : STREAM_ELEMENT_OFFSET;
  sel_stat : SELECTOR_STATUS;
begin
  create_socket( socket );
  bind_socket( socket, address );
  listen_socket( socket );
  accept_socket( socket, sock, address );
  --I wish I could do this
  --accept_socket( socket, sock, address, timeout =3D> 2.0, status =3D> sel=
_stat );
  ...
  loop
    receive_socket( sock, data, last );
    ...
  end loop;
  close_socket( socket );
end;

Thanks,
Matt