###poor man's port scanner###
#must support /dev/tcp -- use BASH
#check port
echo > /dev/tcp/127.0.0.1/8 && echo "Port is open" ||echo "Port is closed"

#avoid errors on closed ports
(echo > /dev/tcp/127.0.0.1/8) 2> /dev/null && echo "Port is open" ||echo "Port is closed"

#scan many ports
for i in {20..10000};
do 
  (echo > /dev/tcp/127.0.0.1/$i) &>/dev/null &&
  echo "Port $i is open";
done

#as oneliner
for i in {20..10000};do (echo > /dev/tcp/127.0.0.1/$i) &>/dev/null && echo "Port $i is open";done