Games::FrozenBubble::NetDiscover(3pm)

Frozen-Bubble
Copyright © 2010 The Frozen-Bubble Team

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2, as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

NAME
Games::FrozenBubble::NetDiscover - high performance server discovery plugin for frozen bubble

SYNOPSIS
    my $discover = Games::FrozenBubble::NetDiscover->new(
        { host => "1.2.3.4", port => 1511 },
        { host => "5.6.7.8", port => 1512 }, ...);
    while($discover->pending()) {
        my @servers = $discover->found();
        for(my $server = 0; $server < @servers; $server++) {
            printf("%02i: ip %s ping %i\n",
                $server, $servers[$server]{ip}, $servers[$server]{ping});
        }
        $discover->work(0.1); # sit in a select loop for 100ms

        # update your screen, and all of that stuff, here.
    }

DESCRIPTION
Games::FrozenBubble::NetDiscover checks a list of servers, finding their versions, ping times, and number of current clients. It uses nonblocking IO and select, to connect to multiple servers in parallel, thus reducing the total amount of time elapsed. This, in turn, allows the user to begin playing frozen bubble more quickly. :)

This module is designed to be called from a GUI loop. It has to spend sit in a select loop for most of its life in order to get accurate ping times, but it will return back to your loop at intervals you specify, so you can check for keystrokes and refresh the screen and so forth.

In order to get consistent results on slow dialup links, this module will only attempt to connect to one server per each 200ms. This means for 18 servers that there are 3.4 seconds of extra guaranteed lag, but it also means packets from multiple servers are less likely to bump into eachother in the queue, so ping reply times will be more reliable.

In the source script, there are two configuration parameters: $number_of_pings and $time_between_connections. These are set to 2 and 0.2, respectively. These two parameters will determine the amount of bandwidth used, and the amount of time taken before the user can select a server. Assuming the user's internet connection can handle the traffic without extra latency from queueing or retransmissions, the worst case latency will be, in seconds:

    N*L + T*(S-1)

where

    N = $number_of_pings
    L = the roundtrip time of the slowest server in the list, in seconds
    T = $time_between_connections
    S = the number of servers in the list

CONSTRUCTOR
    ...->new ({host => "server1", port => port}, {host => "server2", port => port}, ...)

Takes a list of servers as arguments. Each server argument should be a hash reference, consisting of {host => host, port => port}. Returns a Games::FrozenBubble::NetDiscover object, which can be used within a GUI loop to discover all of your servers.

The host string should ideally be an IP address. A hostname string should work too, but DNS lookups will introduce extra, unpredictable latency later on.

METHODS
These methods define the public API for instances of this class.

  found
Returns a list of 0 or more servers found. Each return value is a hash reference, containing the following keys:

    host: the IP address of the server
    port: the TCP port of the server
    pingtimes: array reference, contains the actual result times of 4 pings
    ping: the average roundtrip latency of the server, in ms
    freenicks: the list of players connected
    freegames: the list of open games (not yet started)
    free: the number of idle clients connected to this server
    games: the number of clients connected to this server, who are playing games
    playing: the list of players in games
    geolocs: the geolocations of players in games
    name: the self-proclaimed "name" reported by the server
    language: the preferred language reported by the server

  pending
Returns non-zero if we are still waiting for a response from one or more servers; returns 0 if processing is complete.

  work(seconds)
Enters the main loop of this module. This method requires one argument, a numeric count of seconds to work for. This is expected to be a floating point decimal, for sub-second precision. Returns the number of servers pending, just like the pending method does.

INTERNAL METHODS
These methods are only meant to be called from within the module. They are subject to change without notice.

  try_connect
Attempts to connect to a server. Moves the first "not_started" server to the "pending" list, and creates a non-blocking IO::Socket::INET object for it. Updates the begin_time timestamp, to determine when the next server should be connected.

  server_sm(connection_number)
Implements a simple state machine. Called with an index into the pending array, to indicate that data is available for reading from this server.

  give_up_on(connection_number, reason)
Called if select reports a socket as has_exception. Also called if the server has a bogus version, times out, or we can't parse the IP address or something. Removes the entry from further processing, and emits an error message on stderr.

EXPORT
None.

BUGS
implement some sort of timeout, for servers which don't respond within 5 seconds.

AUTHOR
Mark Glines, <mark@glines.org>.

COPYRIGHT AND LICENSE
This code is donated to the frozen bubble project, www.frozen-bubble.org, so they can do whatever they want with it. Copyright is therefore assigned to those guys.