NAME Net::Server - Extensible, general Perl server engine SYNOPSIS use Net::Server; @ISA = qw(Net::Server); sub process_request { #...code... } Net::Server->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 --------------- MyPackage->run(); exit; package MyPackage; use strict; use vars qw(@ISA); use Net::Server::PreFork; # any personality will do @ISA = qw(Net::Server::PreFork); 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( ){ s/\r?\n$//; print "You said \"$_\"\r\n"; alarm($timeout); } alarm($previous_alarm); }; if( $@=~/timed out/i ){ print STDOUT "Timed Out.\r\n"; return; } } 1; #--------------- file test.pl --------------- Playing this file from the command line will invoke a Net::Server using the PreFork personality. When building a server layer over the Net::Server, it is important to use features such as timeouts to prevent Denial of Service attacks. ARGUMENTS There are four possible ways to pass arguments to Net::Server. They are *passing on command line*, *using a conf file*, *passing parameters to run*, or *using a prebuilt object to call the run method*. Arguments consist of key value pairs. On the commandline these pairs follow the POSIX fashion of `--key value' or `--key=value', and also `key=value'. In the conf file the parameter passing can best be shown by the following regular expression: ($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. 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. log_file Name of log file to be written to. If no name is given and hook is not overridden, log goes to STDERR. pid_file Filename to store pid of parent process. Generally applies only to forking servers. Default is none. 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 protocal 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". host Local host or addr upon which to bind port. proto Protocol to use when binding ports. listen See L 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. 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 close. chroot Directory to chroot to after bind process has taken place and the server is still possibly running as root. 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 release itself from the command line. 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 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 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.