Several times, I would know which are the opened ports in my Linux servers (yes I have many Linux servers :p ).
There are two good methods to check what ports are open in Linux :
- nmap : a port scanner
nmap can be used to scan your machine to check opened ports.
Enter the following command to scan your computers machine:
nmap -sS -O 127.0.0.1
Once the scan has finished you will get the following ouput:
Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2005-01-16 05:48 GMT Interesting ports on localhost.localdomain (127.0.0.1): (The 1656 ports scanned but not shown below are in state: closed) PORT STATE SERVICE22/tcp open ssh80/tcp open http443/tcp open https1241/tcp open nessusDevice type: general purposeRunning: Linux 2.4.X|2.5.X|2.6.X OS details: Linux 2.5.25 - 2.6.3 or Gentoo 1.2 Linux 2.4.19 rc1-rc7) Uptime 1.985 days (since Fri Jan 14 06:10:41 2005) Nmap run completed -- 1 IP address (1 host up) scanned in 2.341 seconds
The second method consist in using netstat. netstat can show hidden ports and what programs using them.
Type following command as root:
It will show you the output of something similar to:
Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.1:61931 0.0.0.0:* LISTEN 5277/wish tcp 0 0 127.0.0.1:5335 0.0.0.0:* LISTEN 3920/mDNSResponder tcp 0 0 0.0.0.0:1241 0.0.0.0:* LISTEN 31438/nessusd: wait tcp 0 0 10.0.0.14:32776 220.127.116.11:6667 ESTABLISHED 5062/xchat tcp 0 0 10.0.0.14:45731 18.104.22.168:1863 ESTABLISHED 5277/wish tcp 0 0 10.0.0.14:33009 22.214.171.124:6667 ESTABLISHED 5062/xchat tcp 0 0 :::80 :::* LISTEN 4355/httpd tcp 0 0 :::22 :::* LISTEN 32372/sshd tcp 0 0 :::443 :::* LISTEN 4355/httpd udp 0 0 0.0.0.0:68 0.0.0.0:* 3614/dhclient udp 0 0 0.0.0.0:5353 0.0.0.0:* 3920/mDNSResponder
A quick post certainly, but I hope it would be useful for you.
PS: for more details try google :p
Good Bye ;-)