René Nyffenegger's collection of things on the web

with comments added by Charles Nicholas, for use in CMSC 331
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A webserver with Perl

This is a very simple webserver written in Perl.
It consists of two parts: webserver.pl and http_handler.pl.
webserver.pl is the core, so to speak, that accepts new connections and creates a thread for each connection. http_handler.pl is the file that actually defines what should be done at a request. Currently, http_handler.pl must expose two sub's: http_request_handler and init_webserver_extension.
The port on which the webserver listens, should be set within init_webserver_extension by assigning the port number to the variable $port_listen.

webserver.pl

use strict;
use warnings;

use Socket;      # CKN so that we can work with TCP/IP sockets
use IO::Select;  # CKN so that we can use the select system call
                 # CKN see man select for details
                 # CKN not much use of STDIN, but lots of I/O anyway

use threads;
use threads::shared;


$|  = 1;         # CKN tells perl to flush the output buffer automatically

# The following variables should be set within init_webserver_extension
# CKN the default port for a web server is 80, but requires privileges
# CKN other popular ports for web servers include 1080 and 8080
use vars qw/
 $port_listen
/;


require "http_handler.pl";
init_webserver_extension();

local *S;  # CKN this will be a socket pointer - yes, Perl has pointers, much syntax like C
           # CKN local is like my, but makes a local copy of a global variable, use with care

# CKN open a socket and start listening
socket     (S, PF_INET   , SOCK_STREAM , getprotobyname('tcp')) or die "couldn't open socket: $!";
setsockopt (S, SOL_SOCKET, SO_REUSEADDR, 1);
bind       (S, sockaddr_in($port_listen, INADDR_ANY));
listen     (S, 5)                                               or die "don't hear anything:  $!";

my $ss = IO::Select->new();
$ss -> add (*S);   # CKN lets us do some select ops on the newly opened socket


while(1) {
  my @connections_pending = $ss->can_read();  # CKN once we have a connection request,
  foreach (@connections_pending) {
    my $fh;
    my $remote = accept($fh, $_);     # CKN accept the connection and open a file handler

    my($port,$iaddr) = sockaddr_in($remote);
    my $peeraddress = inet_ntoa($iaddr);

    my $t = threads->create(\&new_connection, $fh);  # CKN spawn off a sub-process
    $t->detach();
  }
}

sub extract_vars {
  my $line = shift;
  my %vars;

  foreach my $part (split '&', $line) {
    $part =~ /^(.*)=(.*)$/;

    my $n = $1;    # CKN get name and value of parameters
    my $v = $2;
  
    $n =~ s/%(..)/chr(hex($1))/eg;
    $v =~ s/%(..)/chr(hex($1))/eg;
    $vars{$n}=$v;
  }

  return \%vars;
}

sub new_connection {
  my $fh = shift;

  binmode $fh;         # CKN this is useful for Unicode files too

  my %req;

  $req{HEADER}={}; 

  my $request_line = <$fh>;
  my $first_line = "";

  while ($request_line ne "\r\n") {
     unless ($request_line) {
       close $fh; 
     }

     chomp $request_line;

     unless ($first_line) {
       $first_line = $request_line;

      my @parts = split(" ", $first_line);
       if (@parts != 3) {
         close $fh;
       }

       $req{METHOD} = $parts[0];
       $req{OBJECT} = $parts[1];
     }
     else {
       my ($name, $value) = split(": ", $request_line);
       $name       = lc $name;
       $req{HEADER}{$name} = $value;
     }

     $request_line = <$fh>;
  }

  http_request_handler($fh, \%req);

  close $fh;
}

http_handler.pl

sub http_request_handler {
  my $fh     =   shift;
  my $req_   =   shift;

  my %req    =   %$req_;

  my %header = %{$req{HEADER}};

  print $fh "HTTP/1.0 200 OK\r\n";
  print $fh "Server: adp perl webserver\r\n";

  #print $fh "content-length: ... \r\n";

  print $fh "\r\n";

  print $fh "<html><h1>hello</h1></html>";

  print $fh "Method: $req{METHOD}<br>";
  print $fh "Object: $req{OBJECT}<br>";

  foreach my $r (keys %header) {
    print $fh $r, " = ", $header{$r} , "<br>";
  }
}

sub init_webserver_extension {
  $port_listen = 8888;
}

1;   # CKN this is the return value that will be sent back when thread ends

Thanks

Thanks to Rob Neild who found out that this server leaked memory without the $t->detach(); after the creation of the thread.

Related Links

HTTP::Daemon