Test if a port on a remote system is reachable (without telnet)

• Netcat is a useful tool:

• nc 127.0.0.1 123 < /dev/null; echo $?
• Nice and verbose

           Single port:

• nc -zv 127.0.0.1 80
  

  Multiple ports:

  nc -zv 127.0.0.1 22 80 8080
  

  Range of ports:

  nc -zv 127.0.0.1 20-30