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.

#!/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.

#!/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.

# 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>