Checking open ports in an IP addresses range with nmap
Network security
Author: Christophe Gevrey
Updated: [udate]
Introduction
Most of port scanners give the ability to check all open ports on one box, but if you want to do the opposite?There is an easy way to check open ports on Linux (or Windows).
For example, you want to check the port 80 on each machine in an IP range like 192.168.1.1 - 192.168.1.254
Or even better, you want to search for all the open ports in this range.
The solution is command line utility nmap. You can find ports for most of the known OS.
How to
If you are running Linux, you probably already have it. To check that, do:
$locate nmap
If you can not find it, download it from
www.insecure.org and install it following the included instruction.Here are some typical examples:
Scan your own machine
$nmap -v localhost
Check the port http of your local network
$nmap -v -p 80 192.168.1.*
Note that complete doc can be found by typing $man nmap on a un*x box.