Task 1.
#!/usr/local/bin/perl5 -w
use Sys::Hostname;

$host = hostname() || die "couldn't get hostname: $!";

$line = <STDIN>;
while ($line) {
    print "$host:", $line; 
    $line = <STDIN>;
}

Task 2

2a. 128.2.194.242   		Solution: % nslookup kittyhawk
2a. kittyhawk.cmcl.cs.cmu.edu  	Solution: % nslookup 128.2.194.242

Task 3.

PEACH.SRV.cs.cmu.edu		internet address = 128.2.242.81
BANANA.SRV.cs.cmu.edu		internet address = 128.2.242.182
MANGO.SRV.cs.cmu.edu		internet address = 128.2.222.180
BLUEBERRY.SRV.cs.cmu.edu	internet address = 128.2.203.61

% nslookup
> set type=ns
> cs.cmu.edu

Task 4.

(4a) There are 5673 hosts in cs.cmu.edu.

% nslookup
% server mango
% ls cs.cmu.edu > hosts

Then edit out the few non-host names (e.g., OBJECT) that identify
subdomains with their own DNS servers.

% wc -l hosts
5673

(4b) 1,822 Intel boxes  	(grep -i intel hosts |wc -l)
(4c) 209 + 176 = 385 Unix boxes	(grep -i intel hosts | grep -i linux wc -l)
				(grep -i intel hosts | grep -i unix wc -l)

Problem 5.

#!/usr/local/bin/perl5 -w
use IO::Socket;

#
# echo server
#

$port = 8000;

# create a TCP listen socket on port $port
$server = IO::Socket::INET->new(LocalPort => $port,
				Type => SOCK_STREAM,
				Reuse => 1,          
				Listen => 10)
    or die "Couldn't listen on port $port: $@\n";

# loop forever waiting for requests
while(1) {

    # wait for a client's connection request	
    $client = $server->accept(); 

    # echo the input back to the client until end of file
    $line = <$client>;
    while ($line) {
	$client->print($line);
	$line = <$client>;
    }

    # close the server side of the connection
    close $client;
}



Extra credit:

#!/usr/local/bin/perl5 -w
use Net::Ping;

# always flush stdout
select((select(STDOUT), $| = 1)[0]); 

#
# read in list of hostname/IP address pairs
#
$up = $down = 0;
$timeout = 1;
while (defined($line = <STDIN>)) {
    chomp($line);
    ($host) = split(" ",$line);
    if (pingecho($host,$timeout)) {
	print ("u");
	$up++;
    }
    else {
	print ("d");
	$down++;
    }
}

# summarize the results
print "\n\n$up up + $down down = ",$up+$down, " total\n";

# end of ping program

Results:
839 up
4834 down
5673 total