Who has port X open?

[ron.peterson at yellowbank.com (Ron Peterson)]

Ron Peterson wrote:
> 
> John Chambers wrote:
> >
> > Not to change the subject or anything, but in the midst  of
> > the deep philosophical debate, does anyone happen to know:
> >
> > How can I tell what program has port X opoen?
> 
> I think maybe the -i option to 'lsof' is what you're looking for?

e.g. from 'lsof -i :80'

COMMAND     PID     USER   FD   TYPE DEVICE SIZE NODE NAME
httpsd     1695     root   16u  IPv4  10836       TCP *:www (LISTEN)
httpsd    14026     root   16u  IPv4  10836       TCP *:www (LISTEN)
httpsd    14027     root   16u  IPv4  10836       TCP *:www (LISTEN)
httpsd    14028     root   16u  IPv4  10836       TCP *:www (LISTEN)
httpsd    14029     root   16u  IPv4  10836       TCP *:www (LISTEN)
httpsd    14030     root   16u  IPv4  10836       TCP *:www (LISTEN)
httpsd    14031     root   16u  IPv4  10836       TCP *:www (LISTEN)
netscape- 15665 rpeterso   26u  IPv4 527744       TCP
pagoda.mtholyoke.edu:39615->images.slashdot.org:www (CLOSE_WAIT)
...etc.

I should mention that because lsof is so tightly coupled to the
underlying OS, if you've rolled your own kernel, you may need to roll
your own lsof.  From the README:

********************************************************************
| The latest release of lsof is always available via anonymous ftp |
| from vic.cc.purdue.edu.  Look in pub/tools/unix/lsof.            |
********************************************************************  

-Ron-
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