Notes

#!/bin/bash

usage() {
echo "Usage: $0 -i <ip> -p <ports> [-v|-vv]"
echo "** Ports format: all|<number>|<number>-<number>|<number>,<number>,..."
echo "** Example: $0 -i 10.1.1.200 -p 1-65535"
}
bannergrab() {
if [ -n "$NC" ]; then
timeout 1 bash -c "echo 'x' | nc $1 $2"
else
timeout 2 bash -c "exec 3<>/dev/tcp/$1/$2; echo EOF>&3; cat<&3"
fi
}
portscan() {
if [ -n "$NC" ]; then
$NC -w 1 -z -v $1 $2 >/dev/null 2>&1
else
timeout 1 bash -c "echo > /dev/tcp/$1/$2" >/dev/null 2>&1
fi
}

while [ "$1" != "" ]; do
case "$1" in
-i | --ip ) ip="$2"; shift;;
-p | --ports ) ports="$2"; shift;;
-v | --verbose ) verbose="true"; shift;;
-vv | --verbose ) verbose="true"; verbose2="true"; ;;
esac
shift
done

NC=`which nc`

[ -z "$ip" ] || [ -z "$ports" ] && usage && exit 1
[ `echo $ports | grep -o '-' | wc -l` -gt 1 ] && usage && exit 1

ports=`echo $ports | tr '[:upper:]' '[:lower:]'`
[ "$ports" = "all" ] && ports="1-65535"

if [ `echo $ports | grep -o '-' | wc -l` -gt 0 ]; then
start=`echo $ports | cut -d '-' -f 1`
end=`echo $ports | cut -d '-' -f 2`
#ports=`seq $start $end`
ports=($(seq $start $end)) # Create array
fi

batch=1000
step=0
opened=""
#nports=`echo $ports | wc -w`
nports=${#ports[@]} # Number of ports
declare -a pids

echo "Starting background portscan: IP = $ip ($nports ports)" &&
echo "---------------------------------------------------"
while [ $step -le $nports ]; do
echo "Scanning from $step to $((step+$batch))"
for p in ${ports[@]:$step:$batch} ; do
portscan $ip $p &
pids[$p]=$!
if [ $verbose ]; then
if [ $(( $p % 100 )) -eq 0 ]; then
echo "($p)"
else
echo -n "."
fi
fi
done
echo "Getting results ..."
for p in ${ports[@]:$step:$batch} ; do
if wait ${pids[$p]}; then
banner=`bannergrab $ip $p 2>/dev/null | base64 -w 0`
opened="$opened,$p"
#echo "($p)"
echo $ip" ["$p"] open"
echo $ip" ["$p"] banner: $banner"
else
[ $verbose2 ] && echo $ip" ["$p"] closed"
fi
done
step=$(($step+$batch))
done

opened=`echo $opened | sed 's/^,//'`
echo "---------------------------------------------------"
echo "Opened ports: $opened"