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Re: Waiting for an event

by pope (Friar)
on Jun 25, 2001 at 13:34 UTC ( #91223=note: print w/replies, xml ) Need Help??

in reply to Waiting for an event

Yes, as bikeNomad suggested, you can use the four-argument select() or IO::Select. This way avoids the so-called busy-waiting by letting the kernel does the scanning of array of file descriptors of interest. Once your socket is ready to read or write, the kernel wakes up your program, which then handles it. Here's a simple client to send HEAD to a httpd:
#!/usr/bin/perl -w use IO::Socket; $|++; my $client = IO::Socket::INET->new( PeerAddr => '', PeerPort => 80, Proto => 'tcp',) or die "Can't connect: $!"; $rin = $rout = $win = $wout = ''; vec($rin, $client->fileno, 1) = 1; vec($win, $client->fileno, 1) = 1; while (1) { if (select($rout = $rin, $wout = $win, undef, 5) > 0) { if (vec($rout, $client->fileno, 1)) { while (<$client>) { print "Client read: $_" } $client->close; } elsif (vec($wout, $client->fileno, 1)) { print $client "HEAD / HTTP/1.0\r\n\r\n"; } } else { exit } }
Using IO::Select is much more convenient since it does the bit-vector works behind the curtain, as well as its nice OO interface.

POE is also good, but it requires you to have some basic knowledge about state machine, otherwise its programming style may be confusing. I'd recommend using JPRIT's Event module if you want to explore the full power of event-driven programming.

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