Get process that bind a port

[Ezra Nugroho]

On Wed, 2005-11-30 at 13:34 -0500, Reuben D. Budiardja wrote:
> On Wednesday 30 November 2005 12:54, STYMA, ROBERT E (ROBERT) wrote:
> > > Hello,
> > > I am playing around with writing a program to bind to socket
> > > / port in my
> > > machine. Often time, I got the message:
> > > bind(): Address already in use
> > >
> > > So my question is, how do I find out which process bind to a
> > > certain port
> > > number ? 
> 
> > The command lsof run as root will tell you a lot of things including
> > who is bound to a port.
> > For example:
> > lsof | grep 2345
> 
> Great. Thanks.
> 
> > Note that on various flavors unix, I have seen the "already in use" message
> > for a short time after a program exits.  That is, start a program which
> > listens on a certain port, exit the program, immediately restart the
> > program.  A quick test says FC4 does not seem to do this.
> 
> The reason I am asking is because I am seeing exactly this on FC 4. It seems 
> that after exiting, the program does not release the port immediately, and 
> hence restarting the program get the "already in use" message, while 'ps aux 
> | grep progname' shows nothing. Maybe I am doing something wrong, ie. the 
> program does not release the port cleanly on exit or something like that ? 
> I'm not sure...
> 

Is this an RPC client-server program?
If it is, it's done intentionally so that any messages that may still
float around have a destination to rest in peace.

Use "select()" socket utility.
It may mean a little extra programming, but it is really rewarding.