Checking Firewall Ports on remote Host with SSH auth

#!/bin/bash
 
 input file format is:  hostname
 USAGE: ./scan_oem_ports_remote_hosts.sh hostfile
 if test 'X'"$1" = 'X'; then
         echo -n "ENter full path and name of file containing host names: ";read file
 else
         file="$1"
 fi
 grep -v "^#" $file|while read host 
 do
         if test 'X'"$host" = 'X'; then
                 echo "Malformed line in input file, skipping, should be name $host"
         else
                 RESULTS=$(ssh -n -q $host "timeout 5 bash -c 'oemap01.mydomain.com:4903  NOT open"}'

           if test "$RESULTS" != "OPEN"; then
                         /usr/bin/dig +short  $host | awk -v ip=$host '{print ip,"   " $NF "  -->oemap01.mydomain.com    4903  NOT open"}'  
           fi  
         fi
 done

Other Tools you can use for the same instead of /dev/tcp 
nc -vz -w5 hostname port (TCP) 
nc -vzu -w5 hostname port (UDP) 

Reference: https://superuser.com/questions/621870/test-if-a-port-on-a-remote-system-is-reachable-without-telnet

https://arunbavera.wordpress.com/category/em13c/