NAME
    Net::Server - Extensible, general Perl server engine

SYNOPSIS
      package MyPackage;

      use Net::Server;
      @ISA = qw(Net::Server);

      sub process_request {
         #...code...
      }

      MyPackage->run();

FEATURES
     * Single Server Mode
     * Inetd Server Mode
     * Preforking Mode
     * Forking Mode
     * Multi port accepts on Single, Preforking, and Forking modes
     * User customizable hooks
     * Chroot ability after bind
     * Change of user and group after bind
     * Basic allow/deny access control
     * Taint clean
     * Written in Perl
     * Protection against buffer overflow
     * Clean process flow
     * Extensibility

DESCRIPTION
    `Net::Server' is an extensible, generic Perl server engine.
    `Net::Server' combines the good properties from `Net::Daemon' (0.34),
    `NetServer::Generic' (1.03), and `Net::FTPServer' (1.0), and also from
    various concepts in the Apache Webserver.

    `Net::Server' attempts to be a generic server as in `Net::Daemon' and
    `NetServer::Generic'. It includes with it the ability to run as an inetd
    process (`Net::Server::INET'), a single connection server (`Net::Server'
    or `Net::Server::Single'), a forking server (`Net::Server::Fork'), or as
    a preforking server (`Net::Server::PreFork'). In all but the inetd type,
    the server provides the ability to connect to one or to multiple server
    ports.

    `Net::Server' uses ideologies of `Net::FTPServer' in order to provide
    extensibility. The additional server types are made possible via
    "personalities" or sub classes of the `Net::Server'. By moving the
    multiple types of servers out of the main `Net::Server' class, the
    `Net::Server' concept is easily extended to other types (in the near
    future, we would like to add a "Thread" personality).

    `Net::Server' borrows several concepts from the Apache Webserver.
    `Net::Server' uses "hooks" to allow custom servers such as SMTP, HTTP,
    POP3, etc. to be layered over the base `Net::Server' class. In addition
    the `Net::Server::PreFork' class borrows concepts of min_start_servers,
    max_servers, and min_waiting servers. `Net::Server::PreFork' also uses
    the concept of an flock serialized accept when accepting on multiple
    ports.

PERSONALITIES
    `Net::Server' is built around a common class (Net::Server) and is
    extended using sub classes, or `personalities'. Each personality
    inherits, overrides, or enhances the base methods of the base class.

    Included with the Net::Server package are several basic personalities,
    each of which has their own use.

    Fork
        Found in the module Net/Server/Fork.pm (see the Net::Server::Fork
        manpage). This server binds to one or more ports and then waits for
        a connection. When a client request is received, the parent forks a
        child, which then handles the client and exits. This is good for
        moderately hit services.

    INET
        Found in the module Net/Server/INET.pm (see the Net::Server::INET
        manpage). This server is designed to be used with inetd. The
        `pre_bind', `bind', `accept', and `post_accept' are all overridden
        as these services are taken care of by the INET daemon.

    MultiType
        Found in the module Net/Server/MultiType.pm (see the
        Net::Server::MultiType manpage). This server has no server
        functionality of its own. It is designed for servers which need a
        simple way to easily switch between different personalities.
        Multiple `server_type' parameters may be given and
        Net::Server::MultiType will cycle through until it finds a class
        that it can use.

    PreFork
        Found in the module Net/Server/PreFork.pm (see the
        Net::Server::PreFork manpage). This server binds to one or more
        ports and then forks `min_servers' child process. The server will
        make sure that at any given time there are `spare_servers' available
        to receive a client request, up to `max_servers'. Each of these
        children will process up to `max_requests' client connections. This
        type is good for a heavily hit site, and should scale well for most
        applications. (Multi port accept is accomplished using flock to
        serialize the children).

    Single
        All methods fall back to Net::Server. This personality is provided
        only as parallelism for Net::Server::MultiType.

    `Net::Server' was partially written to make it easy to add new
    personalities. Using separate modules built upon an open architecture
    allows for easy addition of new features, a separate development
    process, and reduced code bloat in the core module.

SAMPLE
    The following is a very simple server. The main functionality occurs in
    the process_request method call as shown below. Notice the use of
    timeouts to prevent Denial of Service while reading. (Other examples of
    using `Net::Server' can, or will, be included with this distribution).

      #!/usr/bin/perl -w -T
      #--------------- file test.pl ---------------

      package MyPackage;

      use strict;
      use vars qw(@ISA);
      use Net::Server::PreFork; # any personality will do

      @ISA = qw(Net::Server::PreFork);

      MyPackage->run();
      exit;

      ### over-ridden subs below

      sub process_request {
        my $self = shift;
        eval {

          local $SIG{ALRM} = sub { die "Timed Out!\n" };
          my $timeout = 30; # give the user 30 seconds to type a line

          my $previous_alarm = alarm($timeout);
          while( <STDIN> ){
            s/\r?\n$//;
            print "You said \"$_\"\r\n";
            alarm($timeout);
          }
          alarm($previous_alarm);

        };

        if( $@=~/timed out/i ){
          print STDOUT "Timed Out.\r\n";
          return;
        }

      }

      1;

      #--------------- file test.pl ---------------

    Playing this file from the command line will invoke a Net::Server using
    the PreFork personality. When building a server layer over the
    Net::Server, it is important to use features such as timeouts to prevent
    Denial of Service attacks.

ARGUMENTS
    There are four possible ways to pass arguments to Net::Server. They are
    *passing on command line*, *using a conf file*, *passing parameters to
    run*, or *using a pre-built object to call the run method*.

    Arguments consist of key value pairs. On the commandline these pairs
    follow the POSIX fashion of `--key value' or `--key=value', and also
    `key=value'. In the conf file the parameter passing can best be shown by
    the following regular expression: ($key,$val)=~/^(\w+)\s+(\S+?)\s+$/.
    Passing arguments to the run method is done as follows:
    `Net::Server-'run(key1 => 'val1')>. Passing arguments via a prebuilt
    object can best be shown in the following code:

      #!/usr/bin/perl -w -T
      #--------------- file test2.pl ---------------
      package MyPackage;
      use strict;
      use vars (@ISA);
      use Net::Server;
      @ISA = qw(Net::Server);

      my $server = bless {
        key1 => 'val1',
        }, 'MyPackage';

      $server->run();
      #--------------- file test.pl ---------------

    All four methods for passing arguments may be used at the same time.
    Once an argument has been set, it is not over written if another method
    passes the same argument. `Net::Server' will look for arguments in the
    following order:

      1) Arguments contained in the prebuilt object.
      2) Arguments passed on command line.
      3) Arguments passed to the run method.
      4) Arguments passed via a conf file.

    Key/value pairs used by the server are removed by the configuration
    process so that server layers on top of `Net::Server' can pass and read
    their own parameters. Currently, Getopt::Long is not used. The following
    arguments are available in the default `Net::Server' or
    `Net::Server::Single' modules. (Other personalities may use additional
    parameters and may optionally not use parameters from the base class.)

      Key               Value            Default
      conf_file         "filename"       undef

      log_level         0-5              1
      log_file          "filename"       undef
      pid_file          "filename"       undef

      port              \d+              20203
      host              "host"           "localhost"
      proto             "proto"          "tcp"
      listen            \d+              10

      reverse_lookups   1                undef
      allow             /regex/          none
      deny              /regex/          none

      chroot            "directory"      undef
      user              (uid|username)   "nobody"
      group             (gid|group)      "nobody"
      background        1                undef

    conf_file
        Filename from which to read additional key value pair arguments for
        starting the server. Default is undef.

    log_level
        Ranges from 0 to 5 in level. Specifies what level of error will be
        logged. "O" means logging is off. "5" means very verbose. These
        levels should be able to correlate to syslog levels. Default is 1.

    log_file
        Name of log file to be written to. If no name is given and hook is
        not overridden, log goes to STDERR. Default is undef.

    pid_file
        Filename to store pid of parent process. Generally applies only to
        forking servers. Default is none (undef).

    port
        Local port on which to bind. If low port, process must start as
        root. If multiple ports are given, all will be bound at server
        startup. May be of the form `host:port/proto', `host:port', or
        `port', where *host* represents a hostname residing on the local
        box, where *port* represents either the number of the port (eg.
        "80") or the service designation (eg. "http"), and where *proto*
        represents the protocol to be used. If the protocol is not
        specified, *proto* will default to the `proto' specified in the
        arguments. If `proto' is not specified there it will default to
        "tcp". If *host* is not specified, *host* will default to `host'
        specified in the arguments. If `host' is not specified there it will
        default to "localhost". Default port is 20203.

    host
        Local host or addr upon which to bind port. See the IO::Socket
        manpage.

    proto
        Protocol to use when binding ports. See the IO::Socket manpage.

    listen
          See L<IO::Socket>

    reverse_lookups
        Specify whether to lookup the hostname of the connected IP.
        Information is cached in server object under `peerhost' property.
        Default is to not use reverse_lookups (undef).

    allow/deny
        May be specified multiple times. Contains regex to compare to
        incoming peeraddr or peerhost (if reverse_lookups has been enabled).
        If allow or deny options are given, the incoming client must match
        an allow and not match a deny or the client connection will be
        closed. Defaults to empty array refs.

    chroot
        Directory to chroot to after bind process has taken place and the
        server is still running as root. Defaults to undef.

    user
        Userid or username to become after the bind process has occured.
        Defaults to "nobody." If you would like the server to run as root,
        you will have to specify `user' equal to "root".

    group
        Groupid or groupname to become after the bind process has occured.
        Defaults to "nobody." If you would like the server to run as root,
        you will have to specify `group' equal to "root".

    background
        Specifies whether or not the server should fork after the bind
        method to release itself from the command line. Defaults to undef.

PROPERTIES
    All of the `ARGUMENTS' listed above become properties of the server
    object under the same name. These properties, as well as other internal
    properties, are available during hooks and other method calls.

    The structure of a Net::Server object is shown below:

      $self = bless( {
                       'server' => {
                                     'key1' => 'val1',
                                     # more key/vals
                                   }
                     }, 'Net::Server' );

    This structure was chosen so that all server related properties are
    grouped under a single key of the object hashref. This is so that other
    objects could layer on top of the Net::Server object class and still
    have a fairly clean namespace in the hashref.

    You may get and set properties in two ways. The suggested way is to
    access properties directly via

     my $val = $self->{server}->{key1};

    Accessing the properties directly will speed the server process. A
    second way has been provided for object oriented types who believe in
    methods. The second way consists of the following methods:

      my $val = $self->get_property( 'key1' );
      my $self->set_property( key1 => 'val1' );

    Properties are allowed to be changed at any time with caution (please do
    not undef the sock property or you will close the client connection).

CONFIGURATION FILE
    `Net::Server' allows for the use of a configuration file to read in
    server parameters. The format of this conf file is simple key value
    pairs. Comments and white space are ignored.

      #-------------- file test.conf --------------

      ### user and group to become
      user        somebody
      group       everybody

      ### logging ?
      log_file    /var/log/server.log
      log_level   3
      pid_file    /tmp/server.pid

      ### access control
      allow       .+\.(net|com)
      allow       domain\.com
      deny        a.+

      ### background the process?
      background  1

      ### ports to bind (this should bind
      ### 127.0.0.1:20205 and localhost:20204)
      host        127.0.0.1
      port        localhost:20204
      port        20205

      ### reverse lookups ?
      # reverse_lookups on
 
      #-------------- file test.conf --------------

PROCESS FLOW
    The process flow is written in an open, easy to override, easy to hook,
    fashion. The basic flow is shown below.

      $self->configure_hook;

      $self->configure(@_);

      $self->post_configure;

      $self->post_configure_hook;

      $self->pre_bind;

      $self->bind;

      $self->post_bind_hook;

      $self->post_bind;

      $self->pre_loop_hook;

      $self->loop;

      ### routines inside a standard $self->loop
      # $self->accept;
      # $self->run_client_connection;
      # $self->done;

      $self->pre_server_close_hook;

      $self->server_close;

    The server then exits.

    During the client processing phase (`$self->run_client_connection'), the
    following represents the program flow:

      $self->post_accept;

      $self->get_client_info;

      $self->post_accept_hook;

      if( $self->allow_deny

          && $self->allow_deny_hook ){
    
        $self->process_request;

      }else{

        $self->request_denied_hook;

      }

      $self->post_process_request_hook;

      $self->post_process_request;

    The process then loops and waits for the next connection. For a more in
    depth discussion, please read the code.

HOOKS
    `Net::Server' provides a number of "hooks" allowing for servers layered
    on top of `Net::Server' to respond at different levels of execution.

    `$self->configure_hook()'
        This hook takes place immediately after the `->run()' method is
        called. This hook allows for setting up the object before any built
        in configuration takes place. This allows for custom
        configurability.

    `$self->post_configure_hook()'
        This hook occurs just after the reading of configuration parameters
        and initiation of logging and pid_file creation. It also occurs
        before the `->pre_bind()' and `->bind()' methods are called. This
        hook allows for verifying configuration parameters.

    `$self->post_bind_hook()'
        This hook occurs just after the bind process and just before any
        chrooting, change of user, or change of group occurs. At this point
        the process will still be running as the user who started the
        server.

    `$self->pre_loop_hook()'
        This hook occurs after chroot, change of user, and change of group
        has occured. It allows for preparation before looping begins.

    `$self->post_accept_hook()'
        This hook occurs after a client has connected to the server. At this
        point STDIN and STDOUT are mapped to the client socket. This hook
        occurs before the processing of the request.

    `$self->allow_deny_hook()'
        This hook allows for the checking of ip and host information beyond
        the `$self->allow_deny()' routine. If this hook returns 1, the
        client request will be processed, otherwise, the request will be
        denied processing.

    `$self->request_denied_hook()'
        This hook occurs if either the `$self->allow_deny()' or
        `$self->allow_deny_hook()' have taken place.

    `$self->post_process_request_hook()'
        This hook occurs after the processing of the request, but before the
        client connection has been closed.

    `$self->pre_server_close_hook()'
        This hook occurs before the server begins shutting down.

    `$self->write_to_log_hook'
        This hook handles writing to log files. The default hook is to write
        to STDERR, or to the filename contained in the parameter `log_file'.
        The arguments passed are a log level of 0 to 5 (5 being very
        verbose), and a log line. If it is desired to use the syslog, a
        customized hook may be put in place. (A future version may include
        this as a configurable option).

    `$self->fatal_hook'
        This hook occurs when the server has encountered an unrecoverable
        error. Arguments passed are the error message, the package, file,
        and line number. The hook may close the server, but it is suggested
        that it simply return and use the built in shut down features.

TO DO
    There are several tasks to perform before the alpha label can be removed
    from this software:

    Use It
        The best way to further the status of this project is to use it.
        There are immediate plans to use this as a base class in
        implementing some mail servers and banner servers on a high hit
        site.

    Thread Personality
        Some servers offer a threaded server. Create `Net::Server::Thread'
        as a new personality.

    Other Personalities
        Explore any other personalities

    Sig Handling
        Solidify which signals are handled by base class. Possibly catch
        more that are ignored currently.

    `HUP'
        Allow for a clean hup allowing for re-exec and re-read of
        configuration files. This includes multiport mode.

    Net::HTTPServer, etc
        Create various types of servers. Possibly, port exising servers to
        user Net::Server as a base layer.

    More documentation
        Show more examples and explain process flow more.

    Better Tests
        Do better tests during "make test"

FILES
      The following files are installed as part of this
      distribution.

      Net/Server.pm
      Net/Server/Fork.pm
      Net/Server/INET.pm
      Net/Server/MultiType.pm
      Net/Server/PreFork.pm
      Net/Server/Single.pm

AUTHOR
    Paul T. Seamons paul@seamons.com

THANKS
    Thanks to Rob Brown for help with miscellaneous concepts such as
    tracking down the serialized select via flock ala Apache. Thanks to
    Jonathan J. Miner for patching a blatant problem in the reverse lookups.

SEE ALSO
    Please see also the Net::Server::Fork manpage, the Net::Server::INET
    manpage, the Net::Server::PreFork manpage, the Net::Server::MultiType
    manpage, the Net::Server::Single manpage

COPYRIGHT
      Copyright (C) 2001, Paul T Seamons
                          paul@seamons.com
  
      This package may be distributed under the terms of either the
      GNU General Public License 
        or the
      Perl Artistic License

      All rights reserved.

