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From: Torge.Schmidt@arbi.informatik.uni-oldenburg.de (Torge Schmidt)
Subject: asynchronous socket i/o doesn't work
Organization: University of Oldenburg, Germany
Date: Wed, 30 Dec 1992 23:08:18 GMT
Message-ID: <1992Dec30.230633.18551@arbi.Informatik.Uni-Oldenburg.DE>
Sender: news@arbi.Informatik.Uni-Oldenburg.DE
Lines: 145
Hi there!
I'm trying to program an application using asynchronous socket
i/o. I do the work on an ODT 1.1 (= SCO Unix SysV R3.2.2) PC
simultanously to a SPARC 1+ running SunOS 4.1.2.
A data server waits for connections (accept()). If it gets one,
about 4400 byte of data is sent to the data client in one
message. (I tried write()/read() and send()/recv(), both yield
the same result). The data client will be a X-Application, so it
will loop in XNextEvent(). But in regular intervalls, the data
server sends updated infos, which should be received and
processed by the client immediately, hence asynchronous i/o. I
followed the procedure described in 'Network Programmers Guide'
from AT&T (actually, the title is german, so don't be confused, if
you never heard about) and the SunOS-Answerbook (which shows the
same info as given by AT&T). The problem is, the client never
receives the SIGIO (on SunOS) / SIGPOLL (on ODT) signal. If I send the
signal manually to the client, it works for this instance.
Here is an excerpt of the code of the client.
main () {
...
establish_connection(...); /* sets up socket an signal handler
(see below) */
pause(); /* wait for signal */
display_received_data();
...
}
now the interesting part, the socket-initializing-routine:
/*
** Verbindung aufbauen
*/
void
establish_connection (
...
)
{
...
/* Socket bereitstellen */
sock = socket (hostp->h_addrtype, SOCK_STREAM, 0);
if (sock < 0)
FATAL ("establish_connection", "socket", "");
/* i suspected connect() and the first recv() being processed
before the signal handler was set up, so I moved connect() behind
the initialization. no success */
/* Socket non-blocking machen */
/* this should not be necessary, as the client gets informed, when we get
data. Nevertheless, if I remove it, it won't work either */
if (fcntl (sock, F_SETFL, (fcntl (sock, F_GETFL, 0) | O_NDELAY)) == -1)
FATAL ("establish_connection", "fcntl", "setting socket non-blocking");
/* Das Erscheinen von Nachrichten auf dem Socket erkennen */
TESTLOG ("establish_connection", "setting signal handler for asynchronous socket i/o");
signal (
#ifdef sun
SIGIO
#else
SIGPOLL
#endif
, data_arrived /* Handler */
);
/* neither process id (positive pid) nor process group id
(negative pid) worked in the following */
{ int p = - getpid ();
char t [1000];
/* yeah, fcntl (sock, F_SETOWN, p) is the normal way (with
SunOS), but it didn't do it either */
if (ioctl (sock, SIOCSPGRP, (char *) &p) < 0)
FATAL ("establish_connection", "ioctl (SIOCSPGRP)"
, "setting process group id for asynchronous socket i/o");
if (ioctl (sock, SIOCGPGRP, &p))
FATAL ("establish_connection", "ioctl(SIOCGPGRP)"
, "getting process group id for asynchronous socket i/o");
sprintf (t, "process id of socket %d: %d"
, sock, p
);
TESTLOG ("establish_connection()", t);
}
#ifdef sun
if (fcntl (sock, F_SETFL, fcntl (sock, F_GETFL, 0) | FASYNC) < 0)
FATAL ("establish_connection", "fcntl", "enabling asynchronous socket i/o");
#else
{ int on = 1;
if (ioctl (sock, FIOASYNC, &on) < 0)
FATAL ("establish_connection", "ioctl (FIOASYNC)", "enabling asynchronous socket i/o");
/* desperation: trying STREAMS-ioctl()
*/
if (ioctl (sock, I_SETSIG, S_INPUT) < 0)
FATAL ("establish_connection", "ioctl (I_SETSIG)", "enabling asynchronous socket i/o");
}
#endif
/* Verbindung aufbauen */
if (connect(sock, &sock_addr, sizeof (sock_addr)) < 0)
FATAL ("establish_connection", "connect", "");
}
Well, that's it. Any ideas what I am doing wrong? If so, please
reply via email, as I haven't much time these days (guess why).
Thanx and a happy new year,
--
Torge
-----------------------------------------------------------------------------
Torge Schmidt, FB 10 Informatik, Uni Oldenburg, D-2900 Oldenburg
Privat : Stadskanaal 3, D-2804 Lilienthal, 04298/55 33 (Anrufbeantworter!)
InterNet: Torge.Schmidt@arbi.informatik.uni-oldenburg.de IRC/Nightfall: Moram
-----------------------------------------------------------------------------
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