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Full Discussion: determining open ports
Top Forums UNIX for Advanced & Expert Users determining open ports Post 78160 by tom_xx_hu@yahoo on Friday 15th of July 2005 10:36:40 PM
Old 07-15-2005
As always I am a bit lost here.
Port starts from 0 (or 1 I don't remember) all the way up to 32555 (or sth similar). A port allocated by an active process (either serve or client) can be found by netstat. Everything else is not being used and so "available" for a process to allocate.

/etc/services is a differenet thing which may have implication for inetd or xinetd only. A port does not have to be "registered" in this file to be used by a process which has nothing to do with inetd.

There are more than one approaches to block a port. Conventional approach is via tcpwrapper. Now, people are more likely using (soft- or hardware based) firewall such as iptables in Linux.

I hope it answered all of your questions.
 

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micro_proxy(8)						      System Manager's Manual						    micro_proxy(8)

NAME
micro_proxy - really small HTTP/HTTPS proxy SYNOPSIS
micro_proxy DESCRIPTION
micro_proxy is a very small HTTP/HTTPS proxy. It runs from inetd, which means its performance is poor. But for low-traffic sites, it's quite adequate. It implements all the basic features of an HTTP/HTTPS proxy, in only 260 lines of code. To install it, add a line like this to /etc/inetd.conf: webproxy stream tcp nowait nobody /usr/sbin/micro_proxy micro_proxy Make sure the path to the executable is correct. Then add a line like this to /etc/services: webproxy port/tcp Change "port" to the port number you want to use - 3128, or whatever. Then restart inetd by sending it a "HUP" signal, or rebooting. On some systems, inetd has a maximum spawn rate - if you try to run inetd services faster than a certain number of times per minute, it assumed there's either a bug of an attack going on and it shuts down for a few minutes. If you run into this problem - look for syslog messages about too-rapid looping - you'll need to find out how to increase the limit. Unfortunately this varies from OS to OS. On Free- BSD, you add a "-R 10000" flag to inetd's initial command line. On some Linux systems, you can set the limit on a per-service basis in inetd.conf, by changing "nowait" to "nowait.10000". AUTHOR
Copyright (C) 1999 by Jef Poskanzer <jef@mail.acme.com>. All rights reserved. 16 March 1999 micro_proxy(8)
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