[Fwbuilder-discussion] How to test a Firewall

Kees Cook kees at ubuntu.com
Thu Feb 21 01:55:55 UTC 2008


On Wed, Feb 20, 2008 at 12:35:03PM -0800, Jesse Gordon wrote:
> Netcat (the command nc) is also good -- it is like telnet, but it can 
> establish connections either as a client or server, and it can also work 
> in UDP mode like a UDP telnet client and server. It can also port scan, 
> I believe.

Building on Dustin's example, you can also use netcat to listen.  For
example, to listen on port 80:

  nc -l -p 80  

to listen bound to a specific local address:

  nc -l -p 443 -s

"man nc" has all kinds of details, including timeouts, etc.


Kees Cook
Ubuntu Security Team

More information about the ubuntu-server mailing list