496: Advanced Networking and Web Systems
=========================================

Capstone-level exploration of network protocols, server configuration, and early web technologies.

Topics
------

- TCP/IP networking: BOOTP and DHCP protocol implementation
- HTTP server configuration (Apache ``httpd``)
- CGI scripting with Perl
- Network boot infrastructure

Projects
--------

BOOTP/DHCP Client (``496/bootp.c``, ``496/bootp.pl``)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Implements a BOOTP/DHCP client in both C and Perl. Constructs and broadcasts UDP discovery
packets, parses server responses to obtain IP addresses, subnet masks, and gateway
information, and applies the configuration to the local interface.

.. code-block:: perl

   #!/usr/local/bin/perl
   # Perl BOOTP client — broadcast request, parse reply

   $BOOTP_PORT = 67;
   $socket = IO::Socket::INET->new(Proto => 'udp', Broadcast => 1);

   # Build a minimal BOOTP request packet (RFC 951)
   $packet = pack("CCCCNnna4a4a4a4a16a64a128",
       1,          # op:    BOOTREQUEST
       1,          # htype: Ethernet
       6,          # hlen:  MAC address length
       0,          # hops
       $xid,       # transaction ID
       0, 0,       # secs, flags
       $ciaddr, $yiaddr, $siaddr, $giaddr,
       $chaddr, $sname, $file
   );
   send($socket, $packet, 0, $broadcast);

CGI Web Forms (``496/form.pl``, ``496/search.pl``)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Early CGI scripts written in Perl to handle HTML form submissions and implement basic
search functionality. Demonstrates the CGI request/response cycle, query-string parsing,
and dynamic HTML generation predating modern web frameworks.

.. code-block:: perl

   #!/usr/local/bin/perl

   print "Content-type: text/html\n\n";

   # Read POST body from stdin
   read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});

   # Split into name=value pairs and URL-decode each value
   foreach $pair (split(/&/, $buffer)) {
     ($name, $value) = split(/=/, $pair);
     $value =~ tr/+/ /;
     $value =~ s/%([a-fA-F0-9]{2})/pack("C", hex($1))/eg;
     $form{$name} = $value;
   }

   # Validate required fields before processing
   foreach $var (@required_vars) {
     if (!$form{$var}) {
       print "<h1>Error: please fill in the '$var' field.</h1>\n";
       exit;
     }
   }

Apache Configuration (``496/httpd.conf``, ``496/access.conf``, ``496/srm.conf``)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Configuration files for an Apache 1.x HTTP server, including virtual host setup,
directory access control, and MIME type mappings.

.. code-block:: apacheconf

   # httpd.conf — core server settings (NCSA HTTPd / Apache 1.x)
   ServerType  standalone
   Port        90
   ServerRoot  /usr/local/etc/httpd

   # srm.conf — resource map
   DocumentRoot   /usr/local/etc/httpd/htdocs
   DirectoryIndex index.html

   # access.conf — directory access control
   <Directory /usr/local/etc/httpd/htdocs>
       Options Indexes FollowSymLinks
       AllowOverride None
       order allow,deny
       allow from all
   </Directory>