Ahah! printing perldoc IO::Select now...

Researching IO::Select->select()

Changing code...pretty major changes, getting an array of arrays, rather than a singular array in return...gotta handle both the array of handles ready to read, and the array of handles with problems...

Testing code...

...fixing the stupid mistakes...

...forgot the "my" for this scope...

...it runs! but now it doesn't recognize errors on either link :(

...some more debugging...

Okay. Kind of. The first thing I learned about IO::Select::select is that it has to be called differently. When I tried this: (code simplified slightly to show the pertinent parts)

my $links = new IO::Select();
$links->add($mcserver);
$links->add(\*STDIN);
...
while (my @allhandles = $links->select($links, undef, $links) {
[download]

the select call didn't block at all. Every time it hit, it returned an array of three arrays, all of which had no handles in them.

Looking back at the perldoc IO::Select page, it says "Upon error an empty array is returned."

TIP #1: The returned array is not empty. The arrays contained in the returned array are empty.

So now I knew (rather, presumed) there was an error, so back to the docs I went. "'select' is a static method, that is you call it with the package name like 'new'." I finally figured out what that meant...my:

while (my @allhandles = $links->select($links, undef, $links) {
[download]

should have been

while (my @allhandles = IO::Select::select($links, undef, $links) {
[download]

and after I changed that, it blocked properly.

TIP #2: 'Static' methods are called by package name, not by instance. (You probably knew that. I learned the hard way.) ;)

The other thing I changed was how I handled a disappearing client. I figured the error array would report an EOF, telling me the client is no longer present. (It was a nice try...) I did have a sysread like this:

if (sysread $handle, $command, 1024) {
... do stuff
} else {
... client went away...handle it.
}
[download]

I found it is still necessary :)

TIP #3: A closing socket (at least from telnet) is not an error, as far as IO::Select::select is concerned. (Probably a very reasonable thing.)

So now I've got the basics covered (i.e. I'm back to where I started with can_read()), and I've just yanked the ethernet cable to simulate a flaky server. Minutes pass... I take a smoke break. I have the client do things I know will generate traffic to the (disconnected) server. Still, I get no valid errors :(

Bummer.

TIP #4: Just because you learned a lot doesn't mean your code is right...

Maybe there are flags I should be setting? Maybe I need to build a programatic shrine to St. Larry in my code?

ginseng

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