IO::Socket::Timeout(3pm)

Usage

  use IO::Socket::Timeout;
  # creates a standard IO::Socket::INET object, with a connection timeout
  my $socket = IO::Socket::INET->new( Timeout => 2 );
  # enable read and write timeouts on the socket
  IO::Socket::Timeout->enable_timeouts_on($socket);
  # setup the timeouts
  $socket->read_timeout(0.5);
  $socket->write_timeout(0.5);
  # When using the socket:
  use Errno qw(ETIMEDOUT EWOULDBLOCK);
  print $socket "some request";
  my $response = <$socket>;
  if (! $response && ( 0+$! == ETIMEDOUT || 0+$! == EWOULDBLOCK )) {
    die "timeout reading on the socket";
  }

Version

version 0.32

Overview

"IO::Socket" provides a way to set a timeout on the socket, but the timeout will be used only for connection, not for reading / writing operations.

This module provides a way to set a timeout on read / write operations on an "IO::Socket" instance, or any "IO::Socket::*" modules, like "IO::Socket::INET".

Class method

enable_timeouts_on

  IO::Socket::Timeout->enable_timeouts_on($socket);

Given a socket, it'll return it, but will enable read and write timeouts on it. You'll have to use "read_timeout" and "write_timeout" on it later on.

Returns the socket, so that you can chain this method with others.

If the argument is "undef", the method simply returns empty list.

Methods

These methods are to be called on a socket that has been previously passed to "enable_timeouts_on()".

read_timeout

  my $current_timeout = $socket->read_timeout();
  $socket->read_timeout($new_timeout);

Get or set the read timeout value for a socket created with this module.

write_timeout

  my $current_timeout = $socket->write_timeout();
  $socket->write_timeout($new_timeout);

Get or set the write timeout value for a socket created with this module.

disable_timeout

  $socket->disable_timeout;

Disable the read and write timeouts for a socket created with this module.

enable_timeout

  $socket->enable_timeout;

Re-enable the read and write timeouts for a socket created with this module.

timeout_enabled

  my $is_timeout_enabled = $socket->timeout_enabled();
  $socket->timeout_enabled(0);

Get or Set the fact that a socket has timeouts enabled.

When timeout is hit

When a timeout (read, write) is hit on the socket, the function trying to be performed will return "undef" or empty string, and $! will be set to "ETIMEOUT" or "EWOULDBLOCK". You should test for both.

You can import "ETIMEOUT" and "EWOULDBLOCK" by using "POSIX":

  use Errno qw(ETIMEDOUT EWOULDBLOCK);

If you need to retry

If you want to implement a try / wait / retry mechanism, I recommend using a third-party module, like "Action::Retry". Something like this:

  my $socket;
  my $action = Action::Retry->new(
    attempt_code => sub {
        # (re-)create the socket if needed
        if (! $socket) {
          $socket = IO::Socket->new(...);
          IO::Socket::Timeout->enable_timeouts_on($socket);
          $socket->read_timeout(0.5);
        }
        # send the request, read the answer
        $socket->print($_[0]);
        defined(my $answer = $socket->getline)
          or $socket = undef, die $!;
        $answer;
    },
    on_failure_code => sub { die 'aborting, to many retries' },
  );
  my $reply = $action->run('GET mykey');

Options

You can give a list of socket modules names when use-ing this module, so that internally, composed classes needed gets created and loaded at compile time.

  use IO::Socket::Timeout qw(IO::Socket::INET);

Environment variable

Perl_io_socket_timeout_force_select

This module implements timeouts using one of two strategies. If possible (if the operating system is linux, freebsd or mac), it uses "setsockopt()" to set read / write timeouts. Otherwise it uses "select()" before performing socket operations.

To force the use of "select()", you can set PERL_IO_SOCKET_TIMEOUT_FORCE_SELECT to a true value at compile time (typically in a BEGIN block)

Thanks

Thanks to Vincent Pitt, Christian Hansen and Toby Inkster for various help and useful remarks.

Copyright and license

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

Releases

6 releases since Debian 8 (Jessie); the text changed 2 times.