NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/comp/sys/sun/misc/6076

Text File | 1992-12-30 | 4.7 KB | 157 lines

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Newsgroups: comp.sys.sun.misc,comp.unix.bsd,comp.unix.programmer,comp.unix.questions,comp.unix.wizards
Path: sparky!uunet!spool.mu.edu!yale.edu!ira.uka.de!Sirius.dfn.de!rrz.uni-koeln.de!unidui!uniol!Torge.Schmidt
From: [e-mail] (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: <[e-mail]>
Sender: [e-mail]
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

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Torge  Schmidt,  FB  10   Informatik,    Uni  Oldenburg,    D-2900  Oldenburg
Privat  : Stadskanaal 3,  D-2804 Lilienthal,  04298/55 33 (Anrufbeantworter!)
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