NAME
Net::Server - Extensible, general Perl server engine
SYNOPSIS
#!/usr/bin/perl -w -T
package MyPackage;
use Net::Server;
@ISA = qw(Net::Server);
sub process_request {
#...code...
}
MyPackage->run(port => 160);
exit;
OBTAINING
Visit
http://seamons.com/ for the latest version.
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 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.
Multiplex
Found in the module Net/Server/Multiplex.pm (see the
Net::Server::Multiplex manpage). 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 the IO::Multiplex
manpage). 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 the
Net::Server::PreFork manpage). 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 the
Net::Server::PreFork manpage.
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 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 the
Net::Server::PreFork manpage.
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 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 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 the configure_hook.
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 0-4 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
## 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 the Sys::Syslog
manpage.
syslog_ident
Only available if "log_file" is equal to "Sys::Syslog". Id to
prepend on syslog entries. Default is "net_server". See the
Sys::Syslog manpage.
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 the Sys::Syslog manpage.
syslog_facility
Only available if "log_file" is equal to "Sys::Syslog". See the
Sys::Syslog manpage and the syslog manpage. Default is "daemon".
port
See the Net::Server::Proto manpage. 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 the Net::Server::Proto manpage. 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.
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 the Net::Server::Proto manpage. See the IO::Socket
manpage.
proto
See the Net::Server::Proto manpage. Protocol to use when binding
ports. See the IO::Socket manpage. 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).
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.
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
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).
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.+
### 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.
$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();
$self->hup_server;
}
exit;
HOOKS
"Net::Server" provides a number of "hooks" allowing for servers layered
on top of "Net::Server" to respond at different levels of execution.
"$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 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.
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.
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.
Other Personalities
Explore any other personalities
Net::Server::HTTP, etc
Create various types of servers. Possibly, port exising servers to
user Net::Server as a base layer.
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
For RPM installation, download tarball before running these commands in
your _topdir:
rpm -ta SOURCES/Net-Server-*.tar.gz
rpm -ih RPMS/noarch/perl-Net-Server-*.rpm
AUTHOR
Paul T. 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). Rob Brown is also the maintainer for
Net::Server.
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.
SEE ALSO
Please see also the Net::Server::Fork manpage, the Net::Server::INET
manpage, the Net::Server::PreForkSimple manpage, the
Net::Server::PreFork manpage, the Net::Server::MultiType manpage, the
Net::Server::Single manpage
COPYRIGHT
Copyright (C) 2001, Paul T Seamons
paul at seamons.com
http://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.
