#!/usr/bin/perl
use strict;
use warnings;

use Getopt::Long;

# netstats.pl

my $VERSION = 0.04;

# originally posted at http://www.perlmonks.org/?node_id=1140950

# thanks to Discipulus from over at PerlMonks who
# added the original usage output, added the remaining statuses
# and added the Getopt::Long functionality

my $platform = $^O;

my @wanted = qw( ESTABLISHED SYN_SENT SYN_RECV FIN_WAIT1
                 FIN_WAIT2 TIME_WAIT CLOSE CLOSE_WAIT
                 LAST_ACK LISTEN CLOSING UNKNOWN
               );

my %statuses = map { $_=> undef } @wanted;

# platform specific status munging...

my $listen;

if ($platform eq 'MSWin32'){
    $listen = 'LISTENING';
    delete $statuses{LISTEN};
    $statuses{$listen} = undef;
}
else {
    $listen = 'LISTEN';
}

my $given_args = scalar @ARGV;

my $auto = 0;

if (grep {$_ =~ /-a|--auto/ } @ARGV){
    $given_args -= 2;
}

unless ( GetOptions (
        "ESTABLISHED|E" => \$statuses{ESTABLISHED},
        "SYN_SENT|SS" => \$statuses{SYN_SENT},
        "SYN_RECV|SR" => \$statuses{SYN_RECV},
        "FIN_WAIT1|F1" => \$statuses{FIN_WAIT1},
        "FIN_WAIT2|F2" => \$statuses{FIN_WAIT2},
        "TIME_WAIT|TW" => \$statuses{TIME_WAIT},
        "CLOSE|C" => \$statuses{CLOSE},
        "CLOSE_WAIT|CW" => \$statuses{CLOSE_WAIT},
        "LAST_ACK|LA" => \$statuses{LAST_ACK},
        "LISTEN|L" => \$statuses{$listen},
        "CLOSING|CG" => \$statuses{CLOSING},
        "UNKNOWN|U" => \$statuses{UNKNOWN},
        "auto|a=i" => \$auto,
        "help" => \&help,
        )) {
            help();
    }

if ($auto){

    my $clear = $platform eq 'MSWin32'
      ? 'cls'
      : 'clear';

    while (1){
        system($clear);
        netstat();
        sleep($auto);
    }
}
else {
    netstat();
}

sub netstat {

    my @stat = split '\n', `netstat -nat`;

    if ($given_args == 0){map {$statuses{$_}=1} keys  %statuses}

    my %data = map {$_ => 0} keys %statuses;

    for (@stat){
        s/^\s+//;

        my $status;

        if ($platform eq 'MSWin32'){
            $status = (split)[3];
        }
        else {
            $status = (split)[5];
        }

        next if ! $status;

        $data{$status}++ if defined $data{$status};
    }

    map { printf "%10s\t$data{$_}\n ",$_}
        sort grep {defined $statuses{$_}}
        keys %statuses;
}
sub help {
    print "\nUSAGE $0:\n";
    print <<EOF;

OPTIONS:

Options specifies which status will be reported in the output.
Name of status can be given in upper or lower case.

If no options are given all statuses will be printed.

You can use the following option abbreviations:

    -e  for --ESTABLISHED
    -ss for --SYN_SENT
    -sr for --SYN_RECV
    -f1 for --FIN_WAIT1
    -f2 for --FIN_WAIT2
    -tw for --Time_WAIT
    -c  for --CLOSE
    -cw for --CLOSE_WAIT
    -la for --LAST_ACK
    -l  for --LISTEN
    -cg for --CLOSING
    -u  for --UNKNOWN

    -a  for --auto
    -h  for --help

The special -a or --auto parameter takes an integer. This will
cause the program to refresh the screen and output every integer seconds.

Here a brief description of status meanings:

   ESTABLISHED
          The socket has an established connection.
   SYN_SENT
          The socket is actively attempting to establish a connection.
   SYN_RECV
          A connection request has been received from the network.
   FIN_WAIT1
          The socket is closed, and the connection is shutting down.
   FIN_WAIT2
          Connection is closed, and the socket is waiting for  a  shutdown
          from the remote end.
   TIME_WAIT
          The socket is waiting after close to handle packets still in the
          network.
   CLOSE  The socket is not being used.
   CLOSE_WAIT
          The remote end has shut down, waiting for the socket to close.
   LAST_ACK
          The remote end has shut down, and the socket is closed.  Waiting
          for acknowledgement.
   LISTEN The  socket is listening for incoming connections.  Such sockets
          are  not  included  in  the  output  unless  you   specify   the
          --listening (-l) or --all (-a) option.
   CLOSING
          Both  sockets are shut down but we still don't have all our data
          sent.
   UNKNOWN
          The state of the socket is unknown.

You can get further information by calling "perldoc netstats.pl".

EOF
    exit 1;
}