#!/bin/sh
# Consider that perhaps nmap is unavailable to you, but netcat is.
# Netcat has scanning functionality, but it can be a little slow.
# This script will speed things up by running several instances of
# netcat in parallel.
#
#    - Justin Parrott

NUMTHREADS=10
TIMEOUT=3
STARTPORT=1
STOPPORT=1024

usage() {
        echo "usage: $0 [options] host"
        echo " -s startport         Where to start the scanning (integer)"
        echo " -S stopport          Where to stop the scanning (integer)"
        echo " -t numthreads        Number of processes to execute in parallel"
        echo " -w timeout           Timeout per connect (integer)"
        exit 1
}

while getopts s:S:t:w: opt
do
        case $opt in
        s)     STARTPORT="$OPTARG";;
        S)     STOPPORT="$OPTARG";;
        t)     NUMTHREADS="$OPTARG";;
        w)     TIMEOUT="$OPTARG";;
        \?)    usage;;
        esac
done
shift $((OPTIND - 1))

if [ $# -ne 1 ]
then
        usage
fi

HOST="$1"

tcping()
{
        nc -z -w "$to" "$host" "$port"
}

i="$STARTPORT"

running_threads=0
while [ "$i" -le "$STOPPORT" ]
do
        port="$i" host="$HOST" to="$TIMEOUT" tcping &
        running_threads=$((running_threads + 1))
        i=$((i+1))
        if [ $running_threads -eq "$NUMTHREADS" ]
        then
		wait
		running_threads=0
        fi
done

wait