A (very) poor man’s nmap

I cannot install packages in a machine, so i wrote this very basic substitute to nmap called nmap.ksh
 

#!/bin/ksh
 H=$1
 X=0
 L=600
 while [ $X -lt $L ];do
 O=`echo "~." | telnet -r $H $X 2>&1| grep -i connected | wc -l | sed 's/ //g'`
 if [ $O -eq 1 ];then
 echo "port $X open "
 fi
 X=`echo "$X + 1" | bc`
 done