Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I'm going to be sending a socket communications from one computer to another at specific times of the day (ie. 9am, 10am, etc..). I will use IO::Socket with some variation of the code below on the receiver end: 
 use IO::Socket;
 my $socket = new IO::Socket::INET (
   LocalHost => 'host',
   LocalPort => 'portnumber',
   Proto => 'tcp',
   Listen => 1,
);
die "No socket" unless $socket;
 my $connect= $sock->accept();
while($connect) {
   print $_;
}
close($socket);

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As I understand it, the above code will connect to a socket and print out the contents of the what the sender is sending.

My question is: Do I run this script continously using cron or how do I insure that I accept the socket once the sender sends it? Let's say that the sender initiates his socket sometime between 9 and 9:01. Do I have to repeatedly run the above script between those times in order to insure that I receive the socket? Is there a way to have a background process running that would automatically run my script and then accept the socket?

Thanks.

Replies are listed 'Best First'.
Re: Using Sockets
by Zaxo (Archbishop) on Oct 28, 2002 at 01:05 UTC

    It is fairly simple to make your server run as a daemon. See Super Search on 'daemon' for examples. The basic steps are to fork, exit the parent, and in the child close unneeded file handles, become session leader with &POSIX::setsid, change directory to /, and adjust umask to zero.

    Such a daemon should select or use IO::Select to wait for its socket to become readable. The effect is to make the daemon sleep until there is work for it to do.

    After Compline,
    Zaxo

[reply]
      If the AM is on *nix I would also recommend looking at xinetd (the replacement for inetd).

      If the service is going to be used lightly then this would be a simpler to impliment and not require the overhead a full fledged deamon does.



      grep
      Mynd you, mønk bites Kan be pretti nasti...
[reply]
Re: Using Sockets
by fokat (Deacon) on Oct 28, 2002 at 05:57 UTC
    An easier way for your process to become a daemon, is to use Proc::Daemon.

    What I would do, is leave a server (as a daemon) running continuously (it would be blocked in an accept() most of the time). Then have the client "call home" when required, possibly through cron or similar.

    Best regards

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