Perl: How to get IO::Socket::INET timeout after X seconds? - perl

Question

I'm trying to connect to some host, using invalid port, and i want to get timeout after X seconds. How to do that ?
My code:
$sock = new IO::Socket::INET(
PeerAddr => $_[0],
PeerPort => $_[1],
Proto => 'tcp',
Timeout => 2
);

Answer 1

If you check the code you'll see (I copied it from my Ubuntu 10.04) :
my $timeout = ${*$sock}{'io_socket_timeout'};
# my $before = time() if $timeout;
undef $#;
if ($sock->connect(pack_sockaddr_in($rport, $raddr))) {
# ${*$sock}{'io_socket_timeout'} = $timeout;
return $sock;
}
return _error($sock, $!, $# || "Timeout")
unless #raddr;
# if ($timeout) {
# my $new_timeout = $timeout - (time() - $before);
# return _error($sock,
# (exists(&Errno::ETIMEDOUT) ? Errno::ETIMEDOUT() : $EINVAL),
# "Timeout") if $new_timeout <= 0;
# ${*$sock}{'io_socket_timeout'} = $new_timeout;
# }
Apparently the timeout stuff is commented out so that expleins why it is ignored.
I found a post dating from 2003 where this was discussed. One suggestion (at the bottom) was to open the socket in an eval block which gets terminated by an alarm signal :
eval {
local $SIG{ALRM} = sub { die 'Timed Out'; };
alarm 3;
my $sock = IO::Socket::INET->new(
PeerAddr => inet_ntoa( gethostbyname($host) ),
PeerPort => 'whois',
Proto => 'tcp',
## timeout => ,
);
$sock->autoflush;
print $sock "$qry\015\012";
undef $/; $data = <$sock>; $/ = "\n";
alarm 0;
};
alarm 0; # race condition protection
return "Error: timeout." if ( $# && $# =~ /Timed Out/ );
return "Error: Eval corrupted: $#" if $#;
Not very elegant, but if it works...
Let's verify with a slow server and impatient client :
# Impatient Client
use IO::Socket::INET;
$sock = new IO::Socket::INET(
PeerAddr => "localhost",
PeerPort => "10007",
Proto => 'tcp',
Timeout => 2,
);
print <$sock>;
close($sock);
# SlowServer
use IO::Socket::INET;
$sock = new IO::Socket::INET(
LocalAddr => "localhost",
LocalPort => "10007",
Proto => 'tcp',
Listen => 1,
Reuse => 1,
);
$newsock = $sock->accept();
sleep 5;
#while (<$newsock>) {
# print $_;
#}
print $newsock "Some Stuff";
close($newsock);
close($sock);
if we run this:
pti#pti-laptop:~/playpen$ perl server.pl&
[1] 9130
pti#pti-laptop:~/playpen$ time perl test.pl
Some Stuff[1]+ Done perl server.pl
real 0m5.039s
user 0m0.050s
sys 0m0.030s
So it ignores the 2 second timeout and runs for the full 5 seconds.
Now the other impatient client :
use IO::Socket::INET;
eval {
local $SIG{ALRM} = sub { die 'Timed Out'; };
alarm 2;
$sock = new IO::Socket::INET(
PeerAddr => "localhost",
PeerPort => "10007",
Proto => 'tcp',
Timeout => 2,
);
print <$sock>;
close($sock);
alarm 0;
};
alarm 0; # race condition protection
print "Error: timeout." if ( $# && $# =~ /Timed Out/ );
print "Error: Eval corrupted: $#" if $#;
~
and running it :
pti#pti-laptop:~/playpen$ perl server.pl&
[1] 9175
pti#pti-laptop:~/playpen$ time perl test2.pl
Error: timeout.Error: Eval corrupted: Timed Out at test2.pl line 3.
real 0m2.040s
user 0m0.020s
sys 0m0.010s
Yep, this timeouts after 2 seconds as expected.

Answer 2

So much easier is to use the
IO::Socket::Timeout
as per below and it works like a charm.
use IO::Socket::Timeout;
my $socket = IO::Socket::INET->new( Timeout => 2 );
IO::Socket::Timeout->enable_timeouts_on($socket);
$socket->read_timeout(0.5); # These will work
$socket->write_timeout(0.5); # These will work