in reply to 2 problems using sockets perl 5.8 and mod_perl2 on Linux

Hello,

I checked and $nf is set to 1 on my machine. Odd.

I also added code to count the number of times this occurs and it happens thousands of times.

I don't think you understood what sgifford said. When $nf is 1, there is no error. This is exactly what should be expected. You only look at $! to see what the error is after there is an error. The perl variable $! and the related C variable errno do not get reset to 0 when there is a successfull call. They will hold the previous error value until another error happens or the program specificly sets them. The moral is: Don't look at $! to see if there has been an error. Only look at it to see what error occurred after something else indicates that there has indeed been an error.

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Re: Re: 2 problems using sockets perl 5.8 and mod_perl2 on Linux
by rr (Sexton) on Jul 01, 2003 at 14:02 UTC

    Hello,

    Okay, I grok this and removed the 
    if ($!) { 
            print STDERR "ERROR $!\n";
        }

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    I don't understand why even without checking this the loop spins uncontrolably until it times out (notice the use of Time::HiRes).

    What I am observing as that this select loop keeps returning, $nf is set to 1, but there is no file descriptor in $eout, nor in $rout set to 1 and the loop just starts over again. This chomps up CPU and degrades the performance so badly I can't use it for it's intended purpose.

    Is the logic I am using to detect readable or erroring file descriptors perhaps incorrect?

    Thanks -- rr

[reply]
[d/l]
      After much pondering, I think the problem is that you are initializing your bit vectors like this:
      my $rin = 0;

      [download]
      but you should be doing this 
      my $rin = '';

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      When you say: $rin = 0; vec($rin, $fd, 1) = 1;, apparently the 0 is converted to the string "0" before the bit for $fd is set. This means that an extra bit will be set in each of your vectors.

      Personally, I've never understood vec() well enough to want to use it. I always use IO::Select and can_read() rather than that. I highly recommend the IO::Socket and IO::Select methods because they are so easy to use and, I think, less error-prone.

[reply]
[d/l]
[select]

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