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Re: Free TCP/IP port numbers?

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On Sun, Oct 01, 2017 at 01:28:39AM -0400, Gene Heskett wrote:


> > > Assuring that my port is not in this IANA list is not enough to
> > > ensure that my port number will not clash with a port number used by
> > > a Debian package (by default).
> > >
> > > So your answer to my question is wrong.
> > >
> In which case debian should publish the unlisted ports they do use, if 
> for no other reason than to "stake a claim".

"Debian" "should". Gene, you "should" know better ;-)

Want to start with it? Write a script which scans the /etc files in all
Debian packages for network configurations.

What else have folks forgotten here?

 - dynamic port assignments (X, rpc/portmapper: the last is known for
   having conflicted with CUPS in some distant past).

 - semi-dynamic things (e.g. Debian's way to migrate PostgreSQL)

Unfortunately, there's no "perfect" solution for the OP's problem (among
other things because there are other people having the same problem and
solving it the same way).

My advice: start with /etc/services. Find a suitable "hole", far away
from others (note that typical "dynamic" or "semi-dynamic" assignments
tend to cluster around canonical values, e.g. PostgreSQL: 5432, 5433,
5434...). Plan for collissions (this might be something as complicated
as re-trying ports until success plus some "registry" to look up where
things ended or something as simple as "notify the sysadmin", lest she
spends a night debugging the bugger).

- -- tomás
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