Find IP addresses with an open and listening TCP port

find_port.bash

#!/bin/bash

if [[ -z $2 ]]; then
  echo "$0 SUBNET PORT"
  exit -1
fi

CLASSC="$1"
PORT="$2"

RED='\033[0;31m'
GREEN='\033[0;32m'
NC='\033[0m'

for i in {1..254}; do
  IP_ADDR="$CLASSC.$i"
  printf "$IP_ADDR:$PORT"
  nc -G 5 -w 5 "$IP_ADDR" "$PORT" > /dev/null
  [[ $? != 0 ]] && printf "  \t${RED}closed${NC}\n" || printf "  \t${GREEN}OPEN${NC}\n"
done