Hi,

A friend asked me about this problem, and I am stuck, so I'm asking for your help. The following code is taken almost directly from chapter 12 of Advanced Perl Programming (under "Handling Multiple Clients -Multiple Threads of Execution").

# Forking server
use IO::Socket;
use POSIX;

sub REAPER {
  my $stiff;
  while( $stiff=waitpid(-1,WNOHANG)>0) { }
  $SIG{CHLD}=\&REAPER;
}
$SIG{CHLD} = \&REAPER;

$main_sock = new IO::Socket::INET (LocalHost => 'localhost',
                                   LocalPort => 7070,
                                   Listen    => 5,
                                   Proto     => 'tcp',
                                   Reuse     => 1,
                                );
die "Error: $!\n" unless ($main_sock);
while ($new_sock = $main_sock->accept()) {
    $pid = fork();
    die "Cannot fork: $!" unless defined($pid);
    if ($pid == 0) {
        # Child process
        while (defined($buf = <$new_sock>)) {
           # do something with $buf ....
           print $new_sock "You said: $buf\n";
        }
        exit(0);   # Child process exits when it is done.
    } else {
    # Close new socket in the parent
        $new_sock->close;
    }
}
close ($main_sock);
[download]

When I test it by telnetting to port 7070, it works correctly, printing back what I type. But when I close the connection, the server program exits. Some examination seems to indicate that the accept() call is not being restarted after the signal handler returns. If I set the signal handler to 'IGNORE', everything works ok, which is good for our purposes, but now I am curious as to why this does not work.

I also tried explicitly setting the SA_RESTART flag on the SIGCHLD signal, so that it restarts interrupted slow system calls. So I replaced the assignment to $SIG{CHLD} with the following:

$sigset=POSIX::SigSet->new(SIGCHLD);
$sigaction=POSIX::SigAction->new('main::REAPER', $sigset, &POSIX::SA_R
+ESTART);
$osigact=POSIX::SigAction->new;
sigaction(SIGCHLD, $sigaction, $osigact);
[download]

But I get the exact same behavior. I am on Solaris 2.7, with perl 5.005. Any ideas?

Thanks,

--ZZamboni

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