telnet 99.99.99.99 33491
Trying 99.99.99.99...
Connected to 99.99.99.99..
Escape character is '^]'
^]
telnet> close
Connection closed.
As you can see, the above telnet command shows port 33491 is open.
Running NMAP with -PN
on that same IP and port shows it as closed:
root@Ubuntu:~# nmap -PN 99.99.99.99 -p33491
Starting Nmap 5.00 ( http://nmap.org ) at 2011-10-18 18:18 EDT
Interesting ports on xxx.com (99.99.99.99):
PORT STATE SERVICE
33491/tcp filtered unknown
Nmap done: 1 IP address (1 host up) scanned in 2.07 seconds
In the above example, telnet shows the port open, but NMAP shows the port as 'filtered' aka closed.
How can I get NMAP to show open ports for remote hosts (that disable ping)?
Best Answer
You could ask nmap to try a TCP Connect ...