in reply to Can I timeout an accept call?

A snippet would have been nice, but I think the answer is relatively simple - avoid the problem altogether by setting the socket to operate in non-blocking mode with fcntl. Once you've done this, when you call accept on that socket and there is no connection actually waiting there, then it should return undef and set $! to EWOULDBLOCK. 
   use Fcntl qw/F_GETFL, F_SETFL, O_NONBLOCK/;

   $flags = fcntl(SOCK_HANDLE, F_GETFL, 0) 
       or die "Can't get flags for socket: $!";
   $flags = fcntl(SOCK_HANDLE, F_SETFL, $flags | O_NONBLOCK)
       or die "Can't set flags for socket: $!";

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source: Programming Perl 3

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Re: Re: Can I timeout an accept call?
by Declarent (Sexton) on Jun 10, 2002 at 16:09 UTC

    Many thanks to you, Monks!

    After much fiddling with the ideas here, I decided on another way of doing it. Here's what I decided:

    I'm using IO::Socket::INET, so my ports are defaulted to non-blocking. Sadly, that means that as soon as I get any connection from the client, I can get an undef on that port during a pause or after input during the next cycle. So that was out.

    I then set the port to block, and set the Timeout value, but it wouldn't time out for me at accept. Dunno why that is, I'm on *nix, so it should work. *shrug*

    So, I set the thing to block, and after the accept I added: 

    $test=$data_port->peerhost();
if (not defined $test){close_data_port;}

    [download]
    That way, during any client pause, the connection is still open, so peerhost returns it's IP address. When the connection drops, that value goes undef and I call my exit sub.

    Now, my population explosion is under control. Many Thanks!

    Declarent
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[d/l]
      Unfortunately, non-blocking IO isn't as simple as blocking IO. I'm not sure why you say that your sockets are "defaulted to non-blocking" simply by virtue of using IO::Socket::INET. To my knowledge, sockets created from this module are not automatically placed in a non-blocking state unless you explicitly ask for them that way.

      To get around the fact that many of your non-blocking socket calls will immediately return (frequently with 'undef'), you should use IO::Select to detect when a socket has something for you, or when a socket is available to accept data. It's generally safe then to read from or write to a socket such that you won't block, and won't get 'undef' (unless it really means it).

      Unfortunately this logic tends to add a lot of additional complexity to your code. Fortunately, much of this has already been encapsulated in some Perl modules, POE being the most noteworthy.

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