Re: [OT] Port numbers

[joost@topaz.mdcc.cx (Joost Kooij)]

On Thu, Jul 12, 2001 at 12:24:17AM -0500, will trillich wrote:
> How do you determine WHICH NETWORK SERVICES ARE OPEN (active)?
> Try "netstat -a | grep LISTEN". To see numeric values (instead
> of the common names for services using a particular port) then
> try "netstat -na" instead. For more info, look at "man netstat".

As root, you can also use the '-p' option to netstat, to display
the process id/name that is attached to the open port.

> Curious about your NETWORK TRAFFIC? There's a whole bunch of
> ways to monitor it: iptraf, showtraf, netwatch, tcpview, statnet,
> or even
> 	tcpdump | grep 'what you want to see'

tcpdump has its own filter, which is much more effective in 
terms of resource usage.  It actually compiles a filter from
the specification you give it on the command line.  

Example:  
  tcpdump host foo
  tcpdump not port ssh
  tcpdump port 53
  tcpdump arp
  
> 	lsof -i | grep 'LISTEN'

lsof is different from the other tools you mention.  It does not

Cheers,


Joost