Test outgoing open ports

testports.sh

#!/bin/bash

task(){
  LC_ALL=C nc -vzw5 portquiz.net $1 2>&1 | grep -v 'Connection timed out'
}

N=50                               # Specify number of ports to check at once
(
  for port in {1..65535}; do       # Specify port range to check here
    ((i=i%N)); ((i++==0)) && wait
    task "$port" &
  done
)

super useful to test which port is open at my college ;)