#!/bin/bash

RESOLVE=0
TOP="10000"

HELP="$0 [--resolve|-r] [--top|-t N] port1 ... portN"

PORTS=""

while [[ "$1" != "" ]]
do
    if [[ "$1" = "--help" || "$1" = "-h" ]]
    then
        echo $HELP
        exit
    elif [[ "$1" = "--resolve" || "$1" = "-r" ]]
    then
        RESOLVE=1
    elif [[ "$1" = "--top" || "$1" = "-t" ]]
    then
        shift
        TOP=$1
    else
        PORTS="$PORTS $1"
    fi
    shift
done

for port in $PORTS
do

    name=$(egrep "	$port/tcp" /etc/services | awk '{printf $1" "}')

    cat <<EOF
================================================
Port $port ${name:+( $name)}
================================================
EOF

    netstat -an | egrep :"$port " | sed -e 's/::ffff://g' | \
    awk '{print $5}' | awk -F: '{print $1}' | sort | \
    while read addr
    do

        [[ "$addr" = "" ]] && continue

        if [[ "$RESOLVE" = "1" ]]
        then
            host $addr | sed -e 's/\.$//' | awk '{
                if ($4 == "pointer") {
                    print $5;
                } else { 
                    print "'$addr'";
                }
            }'
        else
            echo $addr
        fi
    done | uniq -c | sort -rn | head -$TOP

done