[PLUG] Important trivia question : number of TCP ports available
Anthony Schlemmer
aschlemm at attbi.com
Fri Jan 31 00:10:02 UTC 2003
Each socket connection on a port requires the use of a file descriptor
so realistically you won't be able to have all 64K ports in use at any
one time. The maximum number of ports available on a system is going to
be based on how large the file descriptor table is on a given system.
Also depending on what sort of processes are being run, you also have to
contend with the fact that many programs take up 3 file descriptors by
default...One each for stdin, stdout, and stderr. The number of file
descriptors in use by a given process will go up further if the process
opens other files, sockets, or any other resources that consumes file
descriptors.
Tony
On Thursday 30 January 2003 16:29 pm, John Hampton wrote:
> Michael Rasmussen said:
> >We have a server that's a mail secondary. The primary went down and
> > mail is flooding to the secondary. The machine has at any given
> > moment ~325 to 380 open or half open TCP connections.
>
> <snip>
>
> >Now, should my linux box be able to function well with this many
> > open connections? Is there a way to increase the number that it
> > can keep open while we fix the problem on the primary mail server?
>
> <snip>
>
> As far as I know your box should be able to do fine with that many
> connections opened (provided it's beefy enough). I believe that
> there are 65,536 ports available. The ports < 1024 being privileged
> ports. If your secondary is a p100 with 32 MB RAM, then you might
> have problems keeping a large number of ports open, but on a PIII or
> so with a couple hundred megs of RAM, I think you should be fine.
>
> John Hampton
> Programmer Analyst
> G.I. Joe's, Inc.
> john.hampton at gijoes.com
>
>
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--
Anthony Schlemmer
aschlemm at attbi.com
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