Auto-discovering port scanner in bash

smartportscan.sh

#!/bin/bash

## @author  Jay Goldberg
## @email  jaymgoldberg@gmail.com
## @license  Apache 2.0
## @description  scans above/below given port
## @usage  smartportscan.sh <text file with "<host> <port>" lines
#=======================================================================

#TODO(JSON output mode using jq)
#TODO(option to insert into SQLite)
#TODO(check if port exists in SQLite before scanning it)
#TODO(accept from stdin or file, autodetect)
#TODO(ability to parse CSV in addition to SSV

#if [[ $# -ge 1 &&  -f "$1" ]] && input="$1" || input="/dev/stdin"
#fi

# which ports to scan in addition to whats in the input file
otherports="80 8080 50000 1024"

# how many seconds to wait for a TCP connect
timeout=2

# how many ports the scanner will climb up/down to detect failure
# before it assumes there are no more live ports coming up
maxsequentialfailures=3 

portcheck () {
	local port="$1"
	# first conditional checks for integer, second for range
	if [ $port -eq $port ] 2>/dev/null || [ $port -le 0 -o $port -ge 65535 ]; then
		#TODO(consolidate test using -o flag or (if [[ expression && expression || expression ]] ; then))
		echo "$port is not a valid port number"
		exit 1
	fi
}

portconnect () {
	local host="$1"
	local port="$2"
	timeout ${timeout} bash -c "cat < /dev/null > /dev/tcp/${host}/${port}" 2>/dev/null
	if [ $? -ne 0 ]; then
		return 0
	else
		return 1
	fi
}

scan () {
	local failed=0
	local host=$2
	local port=$3

	case "$1" in 
		up)
		    # scan upward from the specified port
			op=1
			;;
		down)
		    # scan downward from the specified port
			op=-1
			port=$((port+op)) # we should have already scanned this in
			# main()'s call to up() but this is an assumption, we should
			# prob do up/down inside this fn
			;;
	esac
	
	while [ $failed -lt $maxsequentialfailures ]; do
		portconnect $host $port
		if [ $? -ne 0 ]; then
			echo $host:$port success
			port=$(( port + op ))
		else
			echo $host:$port failure
			(( failed++ ))
			port=$(( port + op ))
		fi
	done
}

while read host port; do
    #parsehostport #TODO(detect and handle a URL as well)
	scan up $host $port
	scan down $host $port
	# check 
	if [[ $otherports ]]; then
		for otherport in $otherports; do
		  scan up $host $otherport
          scan down $host $otherport
	    done
	fi
done < "$1"