#!/usr/bin/perl -w
# tailfin.pl - Diagnostic Utility for the 3Com Home Connect Model: 3CR29223
#
# This modem is a goofy looking translucent plastic thing which looks like a shark's tail fin.
#

use IO::Socket;
use strict;

my $port="55555";
my $server="192.168.100.1";
my $LOGFILE = "tailfin.log";
# Subroutines
sub get_field {
    my $num = shift;
    return $num * 3 - 1;
}


# Program Starts Here
my $socket = IO::Socket::INET->new
(
       Proto   => "tcp",
       PeerAddr=> $server,
       PeerPort=> $port,
) or die "Error creating socket";

$socket->autoflush(1);

# Please Excuse The Ratty Code  ;-)
open(MYLOGFILE,">>$LOGFILE");
while(<$socket>){
	my $record = $_;
	my @data = split(/\$/, $record);
	# Log the data for later plotting
	print MYLOGFILE $record ."\n";

	# Grab some of the values
	my $freq =            $data[get_field(1)] / 1000000; # Convert to MHz
	my $qam  =            $data[get_field(2)];
	my $freq_plan =       $data[get_field(3)];
	my $ucd_array =       $data[get_field(4)];
	my $ucd_unicast =     $data[get_field(5)];
	my $up_mod =          $data[get_field(6)];
	my $datarate =        $data[get_field(7)] / 1048576; # Convert to Mbits/sec
	my $power_tx =        $data[get_field(8)];
	my $down_lock =       $data[get_field(18)];
	my $down_interleave = $data[get_field(19)];
	my $power_rx =        $data[get_field(20)];
	my $range_status  =   $data[get_field(21)];
	my $freq_last =       $data[get_field(28)] / 1000000; # Convert to MHz
	my $freq_low =        $data[get_field(29)] / 1000000; # Convert to MHz
	my $freq_high =       $data[get_field(30)] / 1000000; # Convert to MHz
	
	# Print out some values
	print "Frequency: ".$freq." MHz\n";
	print "Expecting: ".$freq_last." MHz\n";
	print "Band: ".$freq_low." MHz - ".$freq_high." MHz\n";
	print "Plan: ".$freq_plan."\n";
	print "Modulation: ".$up_mod." ".$qam."\n";
	print "SubCarrier: ".$ucd_unicast."\n";
	print "Rate: ".$datarate." Mbit/s\n";
	print "TX Energy: ".$power_tx." dBmV\n";
	print "RX Energy: ".$power_rx." dBmV\n";
	print "Status: ".$range_status."\n";
	print "Lock: ".$down_lock."\n";
	print "---------------------------------------\n";
}
close(MYLOGFILE);
__END__

Data stream from modem port 55555 is split on every third $ symbol.
This leaves you with 3 fields seperated by 2 $ symbols.  
  Field 1: Data Position
  Field 2: Data Length
  Field 3: Data Value

Example:
  "1$9$597000000"
    Field 1 has 9 Characters with value of "597000000"
  "$2$6$64 QAM"
     Field 2 has 6 Characters with value of "64 QAM"

Raw Data Dump of a Good Connection:
1$9$597000000$2$6$64 QAM$3$29$US Standard Cable Frequencies$4$11$2#3#4#5#6#1$5$1$2$6$4$QPSK$7$14$2559999.000000$8$9$45.000000$9$12$DHCP SUCCESS$10$12$TFTP SUCCESS$11$11$REG SUCCESS$12$11$BPI SUCCESS$13$38$CM is ALLOWED for CPE Internet Traffic$14$7$2564478$15$8$96070389$16$2$41$17$1$4$18$17$Downstream Locked$19$1$5$20$10$-29.752012$21$15$Ranging Success$22$5$Green$23$5$Green$24$5$Green$25$5$Green$26$5$Green$27$5$Green$28$9$597000000$29$8$91000000$30$9$857000000$

Reformatted Data Dump:
1$9$ 597000000
$2$6$ 64 QAM
$3$29$ US Standard Cable Frequencies
$4$11$ 2#3#4#5#6#1
$5$1$ 2
$6$4$ QPSK
$7$14$ 2559999.000000
$8$9$ 45.000000
$9$12$ DHCP SUCCESS
$10$12$ TFTP SUCCESS
$11$11$ REG SUCCESS
$12$11$ BPI SUCCESS
$13$38$ CM is ALLOWED for CPE Internet Traffic
$14$7$ 2564478
$15$8$ 96070389
$16$2$ 41
$17$1$ 4
$18$17$ Downstream Locked
$19$1$ 5
$20$10$ -29.752012
$21$15$ Ranging Success
$22$5$ Green
$23$5$ Green
$24$5$ Green
$25$5$ Green
$26$5$ Green
$27$5$ Green
$28$9$ 597000000
$29$8$ 91000000
$30$9$ 857000000
$

Description of Fields:
 1 Frequency
 2 QAM Mode
 3 Frequency Plan
 4 Upstream Bandwidth Allocations (# seperated values)
 5 Upstream Channel Descriptor
 6 Upstream Modulation Type
 7 Symbol rate (bits/sec?)
 8 TX Power level (dBmV)
 9 DHCP Status
10 TFTP Status
11 Registration Status
12 Baseline Privacy (Encryption) Status
13 Cable Modem Status (Allowed or Denied onto Internet)
14 Bytes Sent
15 Bytes Received
16 Uncorrectable Errors
17 CRC Errors
18 Downstream Lock status
19 Downstream Interleave
20 RX Power level (dBmV)
21 Upstream Ranging Status
22 Downstream lock LED
23 Ranging LED
24 DHCP Status LED
25 TFTP Status LED
26 Registration Status LED
27 Baseline Privacy (Encryption) Status LED
28 Last Registered Frequency
29 Lowest Tunable Frequency
30 Highest Tunable Frequency