[Xitami] How to find user of port on linux?

[Bob Paddock]

I just buld Xitami on my Mandrake 8.1 linux box.

When I try to start it up it tells me that port 80 and 81 are already in use, 
which is news to me.  How do I find out what is using them?
httpd is not running, and if I try to connect to

http://127.0.0.1:80 I get 'no server found'.

  src/         xibuild.bat
$ ./xitami
Xitami Web Server v2.5b5 (c) 1991-2000 iMatix
Xitami is free software and comes with ABSOLUTELY NO WARRANTY.
You may redistribute this software under certain conditions;
read the file LICENSE.TXT for details. Run 'xitami -h' for help.

2001/12/27 14:19:38: xilrwp: Could not open LRWP port 81
2001/12/27 14:19:38: Port is already used by another server
2001/12/27 14:19:38: smthttp: web server binding to address 192.168.0.1
2001/12/27 14:19:38: smthttp: web server binding to address 192.168.0.2
2001/12/27 14:19:38: smthttp: web server binding to address 127.0.0.1
2001/12/27 14:19:38: smthttp: opening HTTP service on port 80...
2001/12/27 14:19:38: smthttp: could not open port 80
2001/12/27 14:19:38: smthttp: Port is already used by another server
2001/12/27 14:19:38: smthttp: Permission denied

$ ./xitami -b 5000
Xitami Web Server v2.5b5 (c) 1991-2000 iMatix
Xitami is free software and comes with ABSOLUTELY NO WARRANTY.
You may redistribute this software under certain conditions;
read the file LICENSE.TXT for details. Run 'xitami -h' for help.

2001/12/27 14:21:14: xilrwp: ready for LRWP connections on port 5081
2001/12/27 14:21:15: smthttp: web server binding to address 192.168.0.1
2001/12/27 14:21:15: smthttp: web server binding to address 192.168.0.2
2001/12/27 14:21:15: smthttp: web server binding to address 127.0.0.1
2001/12/27 14:21:15: smthttp: opening HTTP service on port 5080...
2001/12/27 14:21:15: smthttp: HTTP service is now running
2001/12/27 14:21:15: smtftpc: opening FTP service on port 5021...
2001/12/27 14:21:15: smtftpc: FTP service is now running