I've recently got bit by doing non-blocking I/O without any sort of buffer checking mechanism. Instead I just keep writing to the filehandle like below:

use IO::Socket::UNIX;

$SIG{INT} = sub { unlink "/tmp/sock" };

$srv = IO::Socket::UNIX->new(Local=>"/tmp/sock", Listen=>1);
while ($sock = $srv->accept) {
  $sock->blocking(0);
  for(1..999){
    $sock->syswrite(sprintf "%03d %s\n", $_, "=" x ($_/10));
  }
  $sock->close;
}

[download]

(Note: the simplified example above doesn't demonstrate why I needed nonblocking).

The full output from the server should be +- 54K. But most of the time the client will only receive +- 12K. With TCP socket instead of Unix, usually only +- 48K.

It is fixed with using select(): 

use IO::Socket::UNIX;
use IO::Select;

$SIG{INT} = sub { unlink "/tmp/sock" };

$srv = IO::Socket::UNIX->new(Local=>"/tmp/sock", Listen=>1);
while ($sock = $srv->accept) {
  $sock->blocking(0);
  $sel = IO::Select->new;
  $sel->add($sock);
  for(1..999){
    do { @ready = $sel->can_write(1) } until @ready;
    $ready[0]->print(sprintf "%03d %s\n", $_, "=" x ($_/10));
  }
  $sock->close;
}

[download]

But I hate having to add those extra lines just to have non-blocking I/O with a single filehandle to work. Is there something simpler like $sock->can_write?

In reply to Non-blocking IO without select()? by dgaramond2

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