To see what ports are open in your Linux box, you can use nmap port scanner or you can use netstat.
nmap can be used with following command:
# nmap -sS -O 127.0.0.1
The answer will be something like:
Starting Nmap 4.11 ( http://www.insecure.org/nmap/ ) at 2010-07-08 11:31 CEST Interesting ports on localhost.localdomain (127.0.0.1): Not shown: 1663 closed ports PORT STATE SERVICE 22/tcp open ssh 25/tcp open smtp 80/tcp open http 110/tcp open pop3 111/tcp open rpcbind 143/tcp open imap 993/tcp open imaps 995/tcp open pop3s 3306/tcp open mysql 8009/tcp open ajp13 8080/tcp open http-proxy 8443/tcp open https-alt No exact OS matches for host (If you know what OS is running on it, see http://www.insecure.org/cgi-bin/nmap-submit.cgi). ...... Uptime 15.472 days (since Wed Jun 23 00:12:46 2010) Nmap finished: 1 IP address (1 host up) scanned in 9.558 seconds
and nmap can be used to scan remote hosts (keep in mind that many admins will notice this as hack attempt). Simple replace 127.0.0.1 with host IP address.
Another way to check open ports is via netstat. Netstat can show hidden ports and programs associated with ports. Simple execute next command as root:
# netstat -nap
The output list can be very long (depending from your network activity).
Note: Use this tips carefully. I’m not responsible for any potential damage…