in reply to Multiple clients to one server

I'm not quite sure why you say your program gets executed many times: the standard method of using IO::Socket is
my $sock=IO::Socket::new(.....);
while (my $conn=$sock->accept) {
  # do something with $conn
}

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That loop is where every now connection is accepted, and it's up to you to manage fresh connections. If the second connection arrives while you are still processing your loop, the sync packet will be kept waiting. Once you call accept, the SYN-ACK packet will be sent to a client. If you wait too long, the TCP timout will take place, and the connection won't be established. Note that by default, accept blocks until there is a connection it can accept.

On the other hand, the cases where your program gets executed many times are when your program is running from inetd - but in that case, your program would read and write STDIN and STDOUT and would not have to deal with IO::Socket.

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Re: Re: Multiple clients to one server
by Anonymous Monk on Apr 06, 2004 at 13:47 UTC
    Thanks for the reply. Let me flush out the design. We use NetView network management system. It receives SNMP traps and automates actions. In this case, when a mainframe connection to one of our clients goes down, it can result in numerous of these traps be generated (between 1 and 5 usually, but sometimes more).

    NetView recieves and processes the trap - firing my client program once for each incoming trap. The client program opens a socket, sends the data (logs it) and terminates. The reciever program is always running, catches the incoming event and makes some business decisions on what to do with it (like logging and paging).

    The snoop I ran (solaris) indicates that the client program kicked the appropriate number of times, and sent the appropriate number of messages but the receiving program only reflects some of the messages. Here is an example:

    (client says he sent these events - might be ugly here)

    $MESSAGE = Mon Apr 5 22:34:56 2004|2|WOK|DOWN|
    $MESSAGE = Mon Apr 5 22:34:57 2004|2|Q20|DOWN|
    $MESSAGE = Mon Apr 5 22:34:57 2004|2|BYS|DOWN|
    $MESSAGE = Mon Apr 5 22:34:57 2004|2|BYU|DOWN|
    $MESSAGE = Mon Apr 5 22:34:58 2004|2|W7C|DOWN|
    $MESSAGE = Mon Apr 5 22:34:58 2004|2|W0I|DOWN|
    $MESSAGE = Mon Apr 5 22:34:58 2004|2|BCU|DOWN|
    $MESSAGE = Mon Apr 5 22:35:12 2004|2|F4A|DOWN|
    $MESSAGE = Mon Apr 5 22:34:58 2004|2|YEG|DOWN|
    $MESSAGE = Mon Apr 5 22:34:58 2004|2|BCM|DOWN|
    $MESSAGE = Mon Apr 5 22:34:58 2004|2|Y3A|DOWN|
    $MESSAGE = Mon Apr 5 22:35:56 2004|3|F4A|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:29 2004|3|Q20|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:31 2004|3|WOK|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:40 2004|3|BYU|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:40 2004|3|YEG|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:40 2004|3|BCM|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:49 2004|3|W0I|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:50 2004|3|W7C|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:50 2004|3|Y3A|ACTIVE|
    $MESSAGE = Mon Apr 5 22:36:50 2004|3|BYS|ACTIVE|
    $MESSAGE = Mon Apr 5 22:37:09 2004|3|BCU|ACTIVE|


    (receiver says he got these messages - but packet trace shows the senders all sent their packets)

    MON APR 5 22:34:56 2004 | <node name omitted> | WOK | DOWN | <customer name omitted> NORTH YORK
    MON APR 5 22:35:12 2004 | <node name omitted> | F4A | DOWN | <customer name omitted> DORVAL
    MON APR 5 22:35:56 2004 | <node name omitted> | F4A | ACTIVE | <customer name omitted> DORVAL
    MON APR 5 22:36:29 2004 | <node name omitted> | Q20 | ACTIVE | <customer name omitted> NORTH YORK
    MON APR 5 22:36:31 2004 | <node name omitted> | WOK | ACTIVE | <customer name omitted> NORTH YORK
    MON APR 5 22:36:40 2004 | <node name omitted> | BYU | ACTIVE | <customer name omitted> NORTH YORK
    MON APR 5 22:36:49 2004 | <node name omitted> | W0I | ACTIVE | <customer name omitted> NORTH YORK
    MON APR 5 22:37:09 2004 | <node name omitted> | BCU | ACTIVE | <customer name omitted> NORTH YORK

    Where my break down (mentally) is: Does the receiver actually have the capability to receive queued requests? Here is my IO:Socket code bit:
    do {
   use IO::Socket;
   my $sock = new IO::Socket::INET (
                        LocalHost => 'localhost',
                        LocalPort => '7070',
                        Proto => 'tcp',
                        Listen => 20,
                        Reuse => 1,
                        );
   die "Could not create socket: $!\n" unless $sock;

#   $sock->autoflush(1);
   my $new_sock = $sock->accept();
   $sock->autoflush(1);

# --------------------------------------------------------------------
+-----
# --- Now process the buffer                                          
+  ---
# --------------------------------------------------------------------
+-----
   while ($BUFFER = <$new_sock>)
   {
   do stuff here

   } else
        {
           #print "$ORIGIN Un-Processed Buffer: $BUFFER\n";
           print ERR_DATA "$ORIGIN Un-Processed Buffer: $BUFFER\n";
         }
}

close($sock);

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    I've left a lot of the code out here for brevity.
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[d/l]

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