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README

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

SYNOPSIS
        #!/usr/bin/perl -w -T
        package MyPackage;

        use base qw(Net::Server);

        sub process_request {
            my $self = shift;
            while (<STDIN>) {
                s/\r?\n$//;
                print "You said \"$_\"\r\n"; # basic echo
                last if /quit/i;
            }
        }

        MyPackage->run(port => 160);

FEATURES
     * Single Server Mode
     * Inetd Server Mode
     * Preforking Simple Mode (PreForkSimple)
     * Preforking Managed Mode (PreFork)
     * Forking Mode
     * Multiplexing Mode using a single process
     * Multi port accepts on Single, Preforking, and Forking modes
     * Simultaneous accept/recv on tcp, udp, and unix sockets
     * Safe signal handling in Fork/PreFork avoids perl signal trouble
     * User customizable hooks
     * Chroot ability after bind
     * Change of user and group after bind
     * Basic allow/deny access control
     * Customized logging (choose Syslog, log_file, or STDERR)
     * HUP able server (clean restarts via sig HUP)
     * Dequeue ability in all Fork and PreFork modes.
     * 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"), a
    preforking server which maintains a constant number of preforked
    children ("Net::Server::PreForkSimple"), or as a managed preforking
    server which maintains the number of children based on server load
    ("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 (PreFork can choose between flock, IPC::Semaphore, and pipe to
    control serialization).

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 Net::Server::Fork). 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 Net::Server::INET). 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
        Net::Server::MultiType). 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.

    Multiplex
        Found in the module Net/Server/Multiplex.pm (see
        Net::Server::Multiplex). This server binds to one or more ports. It
        uses IO::Multiplex to multiplex between waiting for new connections
        and waiting for input on currently established connections. This
        personality is designed to run as one process without forking. The
        "process_request" method is never used but the "mux_input" callback
        is used instead (see also IO::Multiplex). See examples/samplechat.pl
        for an example using most of the features of Net::Server::Multiplex.

    PreForkSimple
        Found in the module Net/Server/PreFork.pm (see
        Net::Server::PreFork). This server binds to one or more ports and
        then forks "max_servers" child process. The server will make sure
        that at any given time there are always "max_servers" available to
        receive a client request. Each of these children will process up to
        "max_requests" client connections. This type is good for a heavily
        hit site that can dedicate max_server processes no matter what the
        load. It should scale well for most applications. Multi port accept
        is accomplished using either flock, IPC::Semaphore, or pipe to
        serialize the children. Serialization may also be switched on for
        single port in order to get around an OS that does not allow
        multiple children to accept at the same time. For a further
        discussion of serialization see Net::Server::PreFork.

    PreFork
        Found in the module Net/Server/PreFork.pm (see
        Net::Server::PreFork). 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 at least "min_spare_servers" but
        not more than "max_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 either flock, IPC::Semaphore, or
        pipe to serialize the children. Serialization may also be switched
        on for single port in order to get around an OS that does not allow
        multiple children to accept at the same time. For a further
        discussion of serialization see Net::Server::PreFork.

    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.

SOCKET ACCESS
    Once started, the Net::Server will take care of binding to port and
    waiting for connections. Once a connection is received, the Net::Server
    will accept on the socket and will store the result (the client
    connection) in $self->{server}->{client}. This property is a Socket
    blessed into the the IO::Socket classes. UDP servers are slightly
    different in that they will perform a recv instead of an accept.

    To make programming easier, during the post_accept phase, STDIN and
    STDOUT are opened to the client connection. This allows for programs to
    be written using <STDIN> and print "out\n" to print to the client
    connection. UDP will require using a ->send call.

SAMPLE CODE
    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 base qw(Net::Server::PreFork); # any personality will do

        MyPackage->run;

        ### 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 five possible ways to pass arguments to Net::Server. They are
    *passing on command line*, *using a conf file*, *passing parameters to
    run*, *returning values in the default_values method*, or *using a
    pre-built object to call the run method* (such as that returned by the
    new method).

    The "options" method is used to determine which arguments the server
    will search for. Any arguments found from the command line, parameters
    passed to run, and arguments found in the conf_file will be matched
    against the keys of the options template. Any commandline parameters
    that do not match will be left in place and can be further processed by
    the server in the various hooks (by looking at @ARGV).

    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 base qw(Net::Server);

        my $server = MyPackage->new({
            key1 => 'val1',
        });

        $server->run;
        #--------------- file test2.pl ---------------

    All five 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.
      5) Arguments set in default_values method.
      6) Arguments set in the configure_hook.

    Each of these levels will override parameters of the same name specified
    in subsequent levels. For example, specifying --setsid=0 on the command
    line will override a value of "setsid 1" in the conf file.

    Note that the configure_hook method doesn't return values to set, but is
    there to allow for setting up configured values before the configure
    method is called.

    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.

ADDING CUSTOM ARGUMENTS
    It is possible to add in your own custom parameters to those parsed by
    Net::Server. The following code shows how this is done:

        sub options {
            my $self     = shift;
            my $prop     = $self->{'server'};
            my $template = shift;

            ### setup options in the parent classes
            $self->SUPER::options($template);

            ### add a single value option
            $prop->{'my_option'} = undef;
            $template->{'my_option'} = \ $prop->{'my_option'};

            ### add a multi value option
            $prop->{'an_arrayref_item'} ||= [];
            $template->{'an_arrayref_item'} = $prop->{'an_arrayref_item'};
        }

    Overriding the "options" method allows for adding your own custom
    fields. A template hashref is passed in, that should then be modified to
    contain an of your custom fields. Fields which are intended to receive a
    single scalar value should have a reference to the destination scalar
    given. Fields which are intended to receive multiple values should
    reference the corresponding destination arrayref.

    You are responsible for validating your custom options once they have
    been parsed. The post_configure_hook is a good place to do your
    validation.

DEFAULT ARGUMENTS FOR Net::Server
    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         0-4                      2
      log_file          (filename|Sys::Syslog)   undef

      ## syslog parameters
      syslog_logsock    (unix|inet)              unix
      syslog_ident      "identity"               "net_server"
      syslog_logopt     (cons|ndelay|nowait|pid) pid
      syslog_facility   \w+                      daemon

      port              \d+                      20203
      host              "host"                   "*"
      proto             (tcp|udp|unix)           "tcp"
      listen            \d+                      SOMAXCONN

      reverse_lookups   1                        undef
      allow             /regex/                  none
      deny              /regex/                  none
      cidr_allow        CIDR                     none
      cidr_deny         CIDR                     none

      ## daemonization parameters
      pid_file          "filename"               undef
      chroot            "directory"              undef
      user              (uid|username)           "nobody"
      group             (gid|group)              "nobody"
      background        1                        undef
      setsid            1                        undef

      no_close_by_child (1|undef)                undef

      ## See Net::Server::Proto::(TCP|UDP|UNIX|etc)
      ## for more sample parameters.

    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 4 in level. Specifies what level of error will be
        logged. "O" means logging is off. "4" means very verbose. These
        levels should be able to correlate to syslog levels. Default is 2.
        These levels correlate to syslog levels as defined by the following
        key/value pairs: 0=>'err', 1=>'warning', 2=>'notice', 3=>'info',
        4=>'debug'.

    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. If the magic
        name "Sys::Syslog" is used, all logging will take place via the
        Sys::Syslog module. If syslog is used the parameters
        "syslog_logsock", "syslog_ident", and "syslog_logopt",and
        "syslog_facility" may also be defined. If a "log_file" is given or
        if "setsid" is set, STDIN and STDOUT will automatically be opened to
        /dev/null and STDERR will be opened to STDOUT. This will prevent any
        output from ending up at the terminal.

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

    syslog_logsock
        Only available if "log_file" is equal to "Sys::Syslog". May be
        either "unix" of "inet". Default is "unix". See Sys::Syslog.

    syslog_ident
        Only available if "log_file" is equal to "Sys::Syslog". Id to
        prepend on syslog entries. Default is "net_server". See Sys::Syslog.

    syslog_logopt
        Only available if "log_file" is equal to "Sys::Syslog". May be
        either zero or more of "pid","cons","ndelay","nowait". Default is
        "pid". See Sys::Syslog.

    syslog_facility
        Only available if "log_file" is equal to "Sys::Syslog". See
        Sys::Syslog and syslog. Default is "daemon".

    port
        See Net::Server::Proto. Local port/socket 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", "port/proto", 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. See Net::Server::Proto. If you are working with unix
        sockets, you may also specify "socket_file|unix" or
        "socket_file|type|unix" where type is SOCK_DGRAM or SOCK_STREAM. 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 "*". Default port is 20203.
        Configuration passed to new or run may be either a scalar containing
        a single port number or an arrayref of ports.

    host
        Local host or addr upon which to bind port. If a value of '*' is
        given, the server will bind that port on all available addresses on
        the box. See Net::Server::Proto. See IO::Socket. Configuration
        passed to new or run may be either a scalar containing a single host
        or an arrayref of hosts - if the hosts array is shorter than the
        ports array, the last host entry will be used to augment the hosts
        arrary to the size of the ports array.

    proto
        See Net::Server::Proto. Protocol to use when binding ports. See
        IO::Socket. As of release 0.70, Net::Server supports tcp, udp, and
        unix. Other types will need to be added later (or custom modules
        extending the Net::Server::Proto class may be used). Configuration
        passed to new or run may be either a scalar containing a single
        proto or an arrayref of protos - if the protos array is shorter than
        the ports array, the last proto entry will be used to augment the
        protos arrary to the size of the ports array.

    listen
          See L<IO::Socket>.  Not used with udp protocol (or UNIX SOCK_DGRAM).

    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.

    cidr_allow/cidr_deny
        May be specified multiple times. Contains a CIDR block to compare to
        incoming peeraddr. If cidr_allow or cidr_deny options are given, the
        incoming client must match a cidr_allow and not match a cidr_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.
        Process will also background if "setsid" is set.

    setsid
        Specifies whether or not the server should fork after the bind
        method to release itself from the command line and then run the
        "POSIX::setsid()" command to truly daemonize. Defaults to undef. If
        a "log_file" is given or if "setsid" is set, STDIN and STDOUT will
        automatically be opened to /dev/null and STDERR will be opened to
        STDOUT. This will prevent any output from ending up at the terminal.

    no_close_by_child
        Boolean. Specifies whether or not a forked child process has
        permission or not to shutdown the entire server process. If set to
        1, the child may NOT signal the parent to shutdown all children.
        Default is undef (not set).

    no_client_stdout
        Boolean. Default undef (not set). Specifies that STDIN and STDOUT
        should not be opened on the client handle once a connection has been
        accepted. By default the Net::Server will open STDIN and STDOUT on
        the client socket making it easier for many types of scripts to read
        directly from and write directly to the socket using normal print
        and read methods. Disabling this is useful on clients that may be
        opening their own connections to STDIN and STDOUT.

        This option has no affect on STDIN and STDOUT which has a magic
        client property that is tied to the already open STDIN and STDOUT.

    leave_children_open_on_hup
        Boolean. Default undef (not set). If set, the parent will not
        attempt to close child processes if the parent receives a SIG HUP.
        The parent will rebind the the open port and begin tracking a fresh
        set of children.

        Children of a Fork server will exit after their current request.
        Children of a Prefork type server will finish the current request
        and then exit.

        Note - the newly restarted parent will start up a fresh set of
        servers on fork servers. The new parent will attempt to keep track
        of the children from the former parent but custom communication
        channels (open pipes from the child to the old parent) will no
        longer be available to the old child processes. New child processes
        will still connect properly to the new parent.

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

      ### optional syslog directive
      ### used in place of log_file above
      #log_file       Sys::Syslog
      #syslog_logsock unix
      #syslog_ident   myserver
      #syslog_logopt  pid|cons

      ### access control
      allow       .+\.(net|com)
      allow       domain\.com
      deny        a.+
      cidr_allow  127.0.0.0/8
      cidr_allow  192.0.2.0/24
      cidr_deny   192.0.2.4/30

      ### background the process?
      background  1

      ### ports to bind (this should bind
      ### 127.0.0.1:20205 and localhost:20204)
      ### See Net::Server::Proto
      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. This is the flow of the
    "$self->run" method.

      $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.

    During the server shutdown phase ("$self->server_close"), the following
    represents the program flow:

      $self->close_children;  # if any

      $self->post_child_cleanup_hook;

      if( Restarting server ){
         $self->restart_close_hook();
         $self->hup_server;
      }

      $self->shutdown_sockets;

      $self->server_exit;

MAIN SERVER METHODS
    "$self->run"
        This method incorporates the main process flow. This flow is listed
        above.

        The method run may be called in any of the following ways.

           MyPackage->run(port => 20201);

           MyPackage->new({port => 20201})->run;

           my $obj = bless {server=>{port => 20201}}, 'MyPackage';
           $obj->run;

        The ->run method should typically be the last method called in a
        server start script (the server will exit at the end of the ->run
        method).

    "$self->configure"
        This method attempts to read configurations from the commandline,
        from the run method call, or from a specified conf_file. All of the
        configured parameters are then stored in the {"server"} property of
        the Server object.

    "$self->post_configure"
        The post_configure hook begins the startup of the server. During
        this method running server instances are checked for, pid_files are
        created, log_files are created, Sys::Syslog is initialized (as
        needed), process backgrounding occurs and the server closes STDIN
        and STDOUT (as needed).

    "$self->pre_bind"
        This method is used to initialize all of the socket objects used by
        the server.

    "$self->bind"
        This method actually binds to the inialized sockets (or rebinds if
        the server has been HUPed).

    "$self->post_bind"
        During this method priveleges are dropped. The INT, TERM, and QUIT
        signals are set to run server_close. Sig PIPE is set to IGNORE. Sig
        CHLD is set to sig_chld. And sig HUP is set to call sig_hup.

        Under the Fork, PreFork, and PreFork simple personalities, these
        signals are registered using Net::Server::SIG to allow for safe
        signal handling.

    "$self->loop"
        During this phase, the server accepts incoming connections. The
        behavior of how the accepting occurs and if a child process handles
        the connection is controlled by what type of Net::Server personality
        the server is using.

        Net::Server and Net::Server single accept only one connection at a
        time.

        Net::Server::INET runs one connection and then exits (for use by
        inetd or xinetd daemons).

        Net::Server::MultiPlex allows for one process to simultaneously
        handle multiple connections (but requires rewriting the
        process_request code to operate in a more "packet-like" manner).

        Net::Server::Fork forks off a new child process for each incoming
        connection.

        Net::Server::PreForkSimple starts up a fixed number of processes
        that all accept on incoming connections.

        Net::Server::PreFork starts up a base number of child processes
        which all accept on incoming connections. The server throttles the
        number of processes running depending upon the number of requests
        coming in (similar to concept to how Apache controls its child
        processes in a PreFork server).

        Read the documentation for each of the types for more information.

    "$self->server_close"
        This method is called once the server has been signaled to end, or
        signaled for the server to restart (via HUP), or the loop method has
        been exited.

        This method takes care of cleaning up any remaining child processes,
        setting appropriate flags on sockets (for HUPing), closing up
        logging, and then closing open sockets.

    "$self->server_exit"
        This method is called at the end of server_close. It calls exit, but
        may be overridden to do other items. At this point all services
        should be shut down.

MAIN CLIENT CONNECTION METHODS
    "$self->run_client_connection"
        This method is run after the server has accepted and received a
        client connection. The full process flow is listed above under
        PROCESS FLOWS. This method takes care of handling each client
        connection.

    "$self->post_accept"
        This method opens STDIN and STDOUT to the client socket. This allows
        any of the methods during the run_client_connection phase to print
        directly to and read directly from the client socket.

    "$self->get_client_info"
        This method looks up information about the client connection such as
        ip address, socket type, and hostname (as needed).

    "$self->allow_deny"
        This method uses the rules defined in the allow and deny
        configuration parameters to determine if the ip address should be
        accepted.

    "$self->process_request"
        This method is intended to handle all of the client communication.
        At this point STDIN and STDOUT are opened to the client, the ip
        address has been verified. The server can then interact with the
        client connection according to whatever API or protocol the server
        is implementing. Note that the stub implementation uses STDIN and
        STDOUT and will not work if the no_client_stdout flag is set.

        This is the main method to override.

        The default method implements a simple echo server that will repeat
        whatever is sent. It will quit the child if "quit" is sent, and will
        exit the server if "exit" is sent.

    "$self->post_process_request"
        This method is used to clean up the client connection and to handle
        any parent/child accounting for the forking servers.

HOOKS
    "Net::Server" provides a number of "hooks" allowing for servers layered
    on top of "Net::Server" to respond at different levels of execution
    without having to "SUPER" class the main built-in methods. The placement
    of the hooks can be seen in the PROCESS FLOW section.

    Almost all of the default hook methods do nothing. To use a hook you
    simply need to override the method in your subclass. For example to add
    your own post_configure_hook you could do something like the following:

        package MyServer;

        sub post_configure_hook {
            my $self = shift;
            my $prop = $self->{'server'};

            # do some validation here
        }

    The following describes the hooks available in the plain Net::Server
    class (other flavors such as Fork or PreFork have additional hooks).

    "$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->can_read_hook()"
        This hook occurs after a socket becomes readible on an
        accept_multi_port request (accept_multi_port is used if there are
        multiple bound ports to accept on, or if the "multi_port"
        configuration parameter is set to true). This hook is intended to
        allow for processing of arbitrary handles added to the IO::Select
        used for the accept_multi_port. These handles could be added during
        the post_bind_hook. No internal support is added for processing
        these handles or adding them to the IO::Socket. Care must be used in
        how much occurs during the can_read_hook as a long response time
        will result in the server being susceptible to DOS attacks. A return
        value of true indicates that the Server should not pass the readible
        handle on to the post_accept and process_request phases.

        It is generally suggested that other avenues be pursued for sending
        messages via sockets not created by the Net::Server.

    "$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 4 (4 being very
        verbose), and a log line. If log_file is equal to "Sys::Syslog",
        then logging will go to Sys::Syslog and will bypass the
        write_to_log_hook.

    "$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.

    "$self->post_child_cleanup_hook"
        This hook occurs in the parent server process after all children
        have been shut down and just before the server either restarts or
        exits. It is intended for additional cleanup of information. At this
        point pid_files and lockfiles still exist.

    "$self->restart_open_hook"
        This hook occurs if a server has been HUPed (restarted via the HUP
        signal. It occurs just before reopening to the filenos of the
        sockets that were already opened.

    "$self->restart_close_hook"
        This hook occurs if a server has been HUPed (restarted via the HUP
        signal. It occurs just before restarting the server via exec.

OTHER METHODS
    "$self->default_values"
        Allow for returning configuration values that will be used if no
        other value could be found.

        Should return a hashref.

            sub default_values {
              return {
                port => 20201,
              };
            }

    "$self->new"
        As of Net::Server 0.91 there is finally a new method. This method
        takes a class name and an argument hashref as parameters. The
        argument hashref becomes the "server" property of the object.

           package MyPackage;
           use base qw(Net::Server);

           my $obj = MyPackage->new({port => 20201});

           # same as

           my $obj = bless {server => {port => 20201}}, 'MyPackage';

    "$self->log"
        Parameters are a log_level and a message.

        If log_level is set to 'Sys::Syslog', the parameters may alternately
        be a log_level, a format string, and format string parameters. (The
        second parameter is assumed to be a format string if additional
        arguments are passed along). Passing arbitrary format strings to
        Sys::Syslog will allow the server to be vulnerable to exploit. The
        server maintainer should make sure that any string treated as a
        format string is controlled.

            # assuming log_file = 'Sys::Syslog'

            $self->log(1, "My Message with %s in it");
            # sends "%s", "My Message with %s in it" to syslog

            $self->log(1, "My Message with %s in it", "Foo");
            # sends "My Message with %s in it", "Foo" to syslog

        If log_file is set to a file (other than Sys::Syslog), the message
        will be appended to the log file by calling the write_to_log_hook.

    "$self->shutdown_sockets"
        This method will close any remaining open sockets. This is called at
        the end of the server_close method.

RESTARTING
    Each of the server personalities (except for INET), support restarting
    via a HUP signal (see "kill -l"). When a HUP is received, the server
    will close children (if any), make sure that sockets are left open, and
    re-exec using the same commandline parameters that initially started the
    server. (Note: for this reason it is important that @ARGV is not
    modified until "->run" is called).

    The Net::Server will attempt to find out the commandline used for
    starting the program. The attempt is made before any configuration files
    or other arguments are processed. The outcome of this attempt is stored
    using the method "->commandline". The stored commandline may also be
    retrieved using the same method name. The stored contents will
    undoubtedly contain Tainted items that will cause the server to die
    during a restart when using the -T flag (Taint mode). As it is
    impossible to arbitrarily decide what is taint safe and what is not, the
    individual program must clean up the tainted items before doing a
    restart.

      sub configure_hook{
        my $self = shift;

        ### see the contents
        my $ref  = $self->commandline;
        use Data::Dumper;
        print Dumper $ref;

        ### arbitrary untainting - VERY dangerous
        my @untainted = map {/(.+)/;$1} @$ref;

        $self->commandline(\@untainted)
      }

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/PreForkSimple.pm
      Net/Server/PreFork.pm
      Net/Server/Single.pm
      Net/Server/Daemonize.pm
      Net/Server/SIG.pm
      Net/Server/Proto.pm
      Net/Server/Proto/*.pm

INSTALL
    Download and extract tarball before running these commands in its base
    directory:

      perl Makefile.PL
      make
      make test
      make install

AUTHOR
    Paul Seamons <paul at seamons.com>

THANKS
    Thanks to Rob Brown (bbb at cpan.org) for help with miscellaneous
    concepts such as tracking down the serialized select via flock ala
    Apache and the reference to IO::Select making multiport servers
    possible. And for researching into allowing sockets to remain open upon
    exec (making HUP possible).

    Thanks to Jonathan J. Miner <miner at doit.wisc.edu> for patching a
    blatant problem in the reverse lookups.

    Thanks to Bennett Todd <bet at rahul.net> for pointing out a problem in
    Solaris 2.5.1 which does not allow multiple children to accept on the
    same port at the same time. Also for showing some sample code from
    Viktor Duchovni which now represents the semaphore option of the
    serialize argument in the PreFork server.

    Thanks to *traveler* and *merlyn* from http://perlmonks.org for pointing
    me in the right direction for determining the protocol used on a socket
    connection.

    Thanks to Jeremy Howard <j+daemonize at howard.fm> for numerous
    suggestions and for work on Net::Server::Daemonize.

    Thanks to Vadim <vadim at hardison.net> for patches to implement
    parent/child communication on PreFork.pm.

    Thanks to Carl Lewis for suggesting "-" in user names.

    Thanks to Slaven Rezic for suggesing Reuse => 1 in Proto::UDP.

    Thanks to Tim Watt for adding udp_broadcast to Proto::UDP.

    Thanks to Christopher A Bongaarts for pointing out problems with the
    Proto::SSL implementation that currently locks around the socket accept
    and the SSL negotiation. See Net::Server::Proto::SSL.

    Thanks to Alessandro Zummo for pointing out various bugs including some
    in configuration, commandline args, and cidr_allow.

    Thanks to various other people for bug fixes over the years. These and
    future thank-you's are available in the Changes file as well as CVS
    comments.

    Thanks to Ben Cohen and tye (on Permonks) for finding and diagnosing
    more correct behavior for dealing with re-opening STDIN and STDOUT on
    the client handles.

    Thanks to Mark Martinec for trouble shooting other problems with STDIN
    and STDOUT (he proposed having a flag that is now the no_client_stdout
    flag).

    Thanks to David (DSCHWEI) on cpan for asking for the nofatal option with
    syslog.

    Thanks to Andreas Kippnick and Peter Beckman for suggesting leaving open
    child connections open during a HUP (this is now available via the
    leave_children_open_on_hup flag).

    Thanks to LUPE on cpan for helping patch HUP with taint on.

    Thanks to Michael Virnstein for fixing a bug in the check_for_dead
    section of PreFork server.

    Thanks to Rob Mueller for patching PreForkSimple to only open lock_file
    once during parent call. This patch should be portable on systems
    supporting flock. Rob also suggested not closing STDIN/STDOUT but
    instead reopening them to /dev/null to prevent spurious warnings. Also
    suggested short circuit in post_accept if in UDP. Also for cleaning up
    some of the child managment code of PreFork.

    Thanks to Mark Martinec for suggesting additional log messages for
    failure during accept.

    Thanks to Bill Nesbitt and Carlos Velasco for pointing out double
    decrement bug in PreFork.pm (rt #21271)

    Thanks to John W. Krahn for pointing out glaring precended with
    non-parened open and ||.

    Thanks to Ricardo Signes for pointing out setuid bug for perl 5.6.1 (rt
    #21262).

    Thanks to Carlos Velasco for updating the Syslog options (rt #21265).

    Thanks to Steven Lembark for pointing out that no_client_stdout wasn't
    working with the Multiplex server.

    Thanks to Peter Beckman for suggesting allowing Sys::SysLog keyworks be
    passed through the ->log method and for suggesting we allow more types
    of characters through in syslog_ident. Also to Peter Beckman for
    pointing out that a poorly setup localhost will cause tests to hang.

    Thanks to Curtis Wilbar for pointing out that the Fork server called
    post_accept_hook twice. Changed to only let the child process call this,
    but added the pre_fork_hook method.

    And just a general Thanks You to everybody who is using Net::Server or
    who has contributed fixes over the years.

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

AUTHOR
      Paul Seamons <paul at seamons.com>
      http://seamons.com/

      Rob Brown <bbb at cpan.org>

LICENSE
      This package may be distributed under the terms of either the
      GNU General Public License
        or the
      Perl Artistic License

      All rights reserved.

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