NAME
   Net::Daemon - Perl extension for portable daemons

SYNOPSIS
     # Create a subclass of Net::Daemon
     require Net::Daemon;
     package MyDaemon;
     @MyDaemon::ISA = qw(Net::Daemon);

     sub Run ($) {
       # This function does the real work; it is invoked whenever a
       # new connection is made.
     }

WARNING
   THIS IS ALPHA SOFTWARE. It is *only* 'Alpha' because the interface (API)
   is not finalised. The Alpha status does not reflect code quality or
   stability.

DESCRIPTION
   Net::Daemon is an abstract base class for implementing portable server
   applications in a very simple way. The module is designed for Perl 5.005
   and threads, but can work with fork() and Perl 5.004.

   The Net::Daemon class offers methods for the most common tasks a daemon
   needs: Starting up, logging, accepting clients, authorization,
   restricting its own environment for security and doing the true work.
   You only have to override those methods that aren't appropriate for you,
   but typically inheriting will safe you a lot of work anyways.

 Constructors

     $server = Net::Daemon->new($attr, $options);

     $connection = $server->Clone($socket);

   Two constructors are available: The new method is called upon startup
   and creates an object that will basically act as an anchor over the
   complete program. It supports command line parsing via the section on
   "Getopt::Long (3)".

   Arguments of new are *$attr*, an hash ref of attributes (see below) and
   *$options* an array ref of options, typically command line arguments
   (for example \@ARGV) that will be passed to Getopt::Long::GetOptions.

   The second constructor is Clone: It is called whenever a client
   connects. It receives the main server object as input and returns a new
   object. This new object will be passed to the methods that finally do
   the true work of communicating with the client. Communication occurs
   over the socket $socket, Clone's argument.

   Possible object attributes and the corresponding command line arguments
   are:

   *catchint* (--nocatchint)
       On some systems, in particular Solaris, the functions accept(),
       read() and so on are not safe against interrupts by signals. For
       example, if the user raises a USR1 signal (as typically used to
       reread config files), then the function returns an error EINTR. If
       the *catchint* option is on (by default it is, use --nocatchint to
       turn this off), then the package will ignore EINTR errors whereever
       possible.

   *chroot* (--chroot=dir)
       (UNIX only) After doing a bind(), change root directory to the given
       directory by doing a chroot(). This is usefull for security
       operations, but it restricts programming a lot. For example, you
       typically have to load external Perl extensions before doing a
       chroot(), or you need to create hard links to Unix sockets. This is
       typically done in the config file, see the --configfile option. See
       also the --group and --user options.

       If you don't know chroot(), think of an FTP server where you can see
       a certain directory tree only after logging in.

   *clients*
       An array ref with a list of clients. Clients are hash refs, the
       attributes *accept* (0 for denying access and 1 for permitting) and
       *mask*, a Perl regular expression for the clients IP number or its
       host name. See the section on "Access control" below.

   *configfile* (--configfile=file)
       Net::Daemon supports the use of config files. These files are
       assumed to contain a single hash ref that overrides the arguments of
       the new method. However, command line arguments in turn take
       precedence over the config file. See the the section on "Config
       File" section below for details on the config file.

   *debug* (--debug)
       Turn debugging mode on. Mainly this asserts that logging messages of
       level "debug" are created.

   *facility* (--facility=mode)
       (UNIX only) Facility to use for the section on "Sys::Syslog (3)".
       The default is daemon.

   *group* (--group=gid)
       After doing a bind(), change the real and effective GID to the
       given. This is usefull, if you want your server to bind to a
       privileged port (<1024), but don't want the server to execute as
       root. See also the --user option.

       GID's can be passed as group names or numeric values.

   *localaddr* (--localaddr=ip)
       By default a daemon is listening to any IP number that a machine
       has. This attribute allows to restrict the server to the given IP
       number.

   *localpath* (--localpath=path)
       If you want to restrict your server to local services only, you'll
       prefer using Unix sockets, if available. In that case you can use
       this option for setting the path of the Unix socket being created.
       This option implies --proto=unix.

   *localport* (--localport=port)
       This attribute sets the port on which the daemon is listening. It
       must be given somehow, as there's no default.

   *logfile* (--logfile=file)
       By default logging messages will be written to the syslog (Unix) or
       to the event log (Windows NT). On other operating systems you need
       to specify a log file. The special value "STDERR" forces logging to
       stderr.

   *loop-child* (--loop-child)
       This option forces creation of a new child for loops. (See the
       *loop-timeout* option.) By default the loops are serialized.

   *loop-timeout* (--loop-timeout=secs)
       Some servers need to take an action from time to time. For example
       the Net::Daemon::Spooler attempts to empty its spooling queue every
       5 minutes. If this option is set to a positive value (zero being the
       default), then the server will call its Loop method every "loop-
       timeout" seconds.

       Don't trust too much on the precision of the interval: It depends on
       a number of factors, in particular the execution time of the Loop()
       method. The loop is implemented by using the *select* function. If
       you need an exact interval, you should better try to use the alarm()
       function and a signal handler. (And don't forget to look at the
       *catchint* option!)

       It is recommended to use the *loop-child* option in conjunction with
       *loop-timeout*.

   *mode* (--mode=modename)
       The Net::Daemon server can run in three different modes, depending
       on the environment.

       If you are running Perl 5.005 and did compile it for threads, then
       the server will create a new thread for each connection. The thread
       will execute the server's Run() method and then terminate. This mode
       is the default, you can force it with "--mode=threads".

       If threads are not available, but you have a working fork(), then
       the server will behave similar by creating a new process for each
       connection. This mode will be used automatically in the absence of
       threads or if you use the "--mode=fork" option.

       Finally there's a single-connection mode: If the server has accepted
       a connection, he will enter the Run() method. No other connections
       are accepted until the Run() method returns. This operation mode is
       usefull if you have neither threads nor fork(), for example on the
       Macintosh. For debugging purposes you can force this mode with "--
       mode=single".

   *options*
       Array ref of Command line options that have been passed to the
       server object via the new method.

   *parent*
       When creating an object with Clone the original object becomes the
       parent of the new object. Objects created with new usually don't
       have a parent, thus this attribute is not set.

   *pidfile* (--pidfile=file)
       (UNIX only) If this option is present, a PID file will be created at
       the given location.

   *proto* (--proto=proto)
       The transport layer to use, by default *tcp* or *unix* for a Unix
       socket. It is not yet possible to combine both.

   *socket*
       The socket that is connected to the client; passed as $client
       argument to the Clone method. If the server object was created with
       new, this attribute can be undef, as long as the Bind method isn't
       called. Sockets are assumed to be IO::Socket objects.

   *user* (--user=uid)
       After doing a bind(), change the real and effective UID to the
       given. This is usefull, if you want your server to bind to a
       privileged port (<1024), but don't want the server to execute as
       root. See also the --group and the --chroot options.

       UID's can be passed as group names or numeric values.

   *version* (--version)
       Supresses startup of the server; instead the version string will be
       printed and the program exits immediately.

   Note that most of these attributes (facility, mode, localaddr,
   localport, pidfile, version) are meaningfull only at startup. If you set
   them later, they will be simply ignored. As almost all attributes have
   appropriate defaults, you will typically use the localport attribute
   only.

 Command Line Parsing

     my $optionsAvailable = Net::Daemon->Options();

     print Net::Daemon->Version(), "\n";

     Net::Daemon->Usage();

   The Options method returns a hash ref of possible command line options.
   The keys are option names, the values are again hash refs with the
   following keys:

   template
       An option template that can be passed to Getopt::Long::GetOptions.

   description
       A description of this option, as used in Usage

   The Usage method prints a list of all possible options and returns. It
   uses the Version method for printing program name and version.

 Config File

   If the config file option is set in the command line options or in the
   in the "new" args, then the method

     $server->ReadConfigFile($file, $options, $args)

   is invoked. By default the config file is expected to contain Perl
   source that returns a hash ref of options. These options override the
   "new" args and will in turn be overwritten by the command line options,
   as present in the $options hash ref.

   A typical config file might look as follows, we use the DBI::ProxyServer
   as an example:

       # Load external modules; this is not required unless you use
       # the chroot() option.
       #require DBD::mysql;
       #require DBD::CSV;

       {
           # 'chroot' => '/var/dbiproxy',
           'facility' => 'daemon',
           'pidfile' => '/var/dbiproxy/dbiproxy.pid',
           'user' => 'nobody',
           'group' => 'nobody',
           'localport' => '1003',
           'mode' => 'fork'

           # Access control
           'clients' => [
               # Accept the local
               {
                   'mask' => '^192\.168\.1\.\d+$',
                   'accept' => 1
               },
               # Accept myhost.company.com
               {
                   'mask' => '^myhost\.company\.com$',
                   'accept' => 1
               }
               # Deny everything else
               {
                   'mask' => '.*',
                   'accept' => 0
               }
           ]
       }

 Access control

   The Net::Daemon package supports a host based access control scheme. By
   default access is open for anyone. However, if you create an attribute
   $self->{'clients'}, typically in the config file, then access control is
   disabled by default. For any connection the client list is processed:
   The clients attribute is an array ref to a list of hash refs. Any of the
   hash refs may contain arbitrary attributes, including the following:

   mask    A Perl regular expression that has to match the clients IP number or
           its host name. The list is processed from the left to the right,
           whenever a 'mask' attribute matches, then the related hash ref
           is choosen as client and processing the client list stops.

   accept  This may be set to true or false (default when omitting the
           attribute), the former means accepting the client.

 Event logging

     $server->Log($level, $format, @args);
     $server->Debug($format, @args);
     $server->Error($format, @args);
     $server->Fatal($format, @args);

   The Log method is an interface to the section on "Sys::Syslog (3)" or
   the section on "Win32::EventLog (3)". It's arguments are *$level*, a
   syslog level like debug, notice or err, a format string in the style of
   printf and the format strings arguments.

   The Debug and Error methods are shorthands for calling Log with a level
   of debug and err, respectively. The Fatal method is like Error, except
   it additionally throws the given message as exception.

   See the Net::Daemon::Log(3) manpage for details.

 Flow of control

     $server->Bind();
     # The following inside Bind():
     if ($connection->Accept()) {
         $connection->Run();
     } else {
         $connection->Log('err', 'Connection refused');
     }

   The Bind method is called by the application when the server should
   start. Typically this can be done right after creating the server object
   $server. Bind usually never returns, except in case of errors.

   When a client connects, the server uses Clone to derive a connection
   object $connection from the server object. A new thread or process is
   created that uses the connection object to call your classes Accept
   method. This method is intended for host authorization and should return
   either FALSE (refuse the client) or TRUE (accept the client).

   If the client is accepted, the Run method is called which does the true
   work. The connection is closed when Run returns and the corresponding
   thread or process exits.

 Error Handling

   All methods are supposed to throw Perl exceptions in case of errors.

MULTITHREADING CONSIDERATIONS
   All methods are working with lexically scoped data and handle data only,
   the exception being the OpenLog method which is invoked before threading
   starts. Thus you are safe as long as you don't share handles between
   threads. I strongly recommend that your application behaves similar.

EXAMPLE
   As an example we'll write a simple calculator server. After connecting
   to this server you may type expressions, one per line. The server
   evaluates the expressions and prints the result. (Note this is an
   example, in real life we'd never implement sucj a security hole. :-)

   For the purpose of example we add a command line option *--base* that
   takes 'hex', 'oct' or 'dec' as values: The servers output will use the
   given base.

     # -*- perl -*-
     #
     # Calculator server
     #
     require 5.004;
     use strict;

     require Net::Daemon;

     package Calculator;

     use vars qw($VERSION @ISA);
     $VERSION = '0.01';
     @ISA = qw(Net::Daemon); # to inherit from Net::Daemon

     sub Version ($) { 'Calculator Example Server, 0.01'; }

     # Add a command line option "--base"
     sub Options ($) {
         my($self) = @_;
         my($options) = $self->SUPER::Options();
         $options->{'base'} = { 'template' => 'base=s',
                                'description' => '--base                  '
                                       . 'dec (default), hex or oct'
                                 };
         $options;
     }

     # Treat command line option in the constructor
     sub new ($$;$) {
         my($class, $attr, $args) = @_;
         my($self) = $class->SUPER::new($attr, $args);
         if ($self->{'parent'}) {
             # Called via Clone()
             $self->{'base'} = $self->{'parent'}->{'base'};
         } else {
             # Initial call
             if ($self->{'options'}  &&  $self->{'options'}->{'base'}) {
                 $self->{'base'} = $self->{'options'}->{'base'}
             }
         }
         if (!$self->{'base'}) {
             $self->{'base'} = 'dec';
         }
         $self;
     }

     sub Run ($) {
         my($self) = @_;
         my($line, $sock);
         $sock = $self->{'socket'};
         while (1) {
             if (!defined($line = $sock->getline())) {
                 if ($sock->error()) {
                     $self->Error("Client connection error %s",
                                  $sock->error());
                 }
                 $sock->close();
                 return;
             }
             $line =~ s/\s+$//; # Remove CRLF
             my($result) = eval $line;
             my($rc);
             if ($self->{'base'} eq 'hex') {
                 $rc = printf $sock ("%x\n", $result);
             } elsif ($self->{'base'} eq 'oct') {
                 $rc = printf $sock ("%o\n", $result);
             } else {
                 $rc = printf $sock ("%d\n", $result);
             }
             if (!$rc) {
                 $self->Error("Client connection error %s",
                              $sock->error());
                 $sock->close();
                 return;
             }
         }
     }

     package main;

     my $server = Calculator->new({'pidfile' => 'none',
                                   'localport' => 2000}, \@ARGV);
     $server->Bind();

AUTHOR AND COPYRIGHT
     Net::Daemon is Copyright (C) 1998, Jochen Wiedmann
                                        Am Eisteich 9
                                        72555 Metzingen
                                        Germany

                                        Phone: +49 7123 14887
                                        Email: [email protected]

     All rights reserved.

     You may distribute this package under the terms of either the GNU
     General Public License or the Artistic License, as specified in the
     Perl README file.

SEE ALSO
   the RPC::pServer(3) manpage, the Netserver::Generic(3) manpage, the
   Net::Daemon::Log(3) manpage, the Net::Daemon::Test(3) manpage

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.