On Friday, August 22, 2003, at 05:52 PM, Dar Scott wrote:
I am able to 'accept' UDP and TCP on OS X as any user.
I didn't realize Linux would have the constraint and am interested in the answer to this.
(My problem is that I have a client/server acting up and I want to see which one is the problem. I want to have some non-Rev service to send a UDP response to see if the client has trouble.)
Forget what I said about 10,000 or higher that was incorrect. Regarding /etc/inetd.conf, /etc/services, TCP and UDP port numbering. An O'Reilly book published in 1991 says:
"It should be noted that a port does not have to be listed in the database to be used. Any program may use any port it wants to (provided it's not already in use), with two exceptions. The ARPANET administration has decreed that port numbers below 512 are reserved for services which it approves. Further, Berkeley UNIX imposes the rule that port numbers below 1024 may only be used by the super-user. Thus, regular user programs are restricted to port numbers between 1025 and 32767."
Note that servers like MySQL and PostgreSQL run as their own user (not as root) and run on high numbered ports for security; 3306 and 5432 respectively.
Some servers like Apache, running on port 80, running as user nobody, must startup as root, and change uid after establishing sockets- or something like that.
Presumably Mac OS X and Linux both follow these guidelines as well. I don't know if Windows has the equivalent concept of "super-user" or if it has the same rules for port usage.
Hope this helps,
Alex Rice, Software Developer Architectural Research Consultants, Inc. http://ARCplanning.com
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