Date: Mon, 01 Dec 2014 17:03:54 +0000 From: Joe Holden <lists@rewt.org.uk> To: freebsd-net@freebsd.org Subject: Re: Can multiple apps listen for TCP on the same port? Message-ID: <547C9F7A.5000803@rewt.org.uk> In-Reply-To: <CAJ-VmokGVnqeY6nm55q2Q83bTc_%2BKsq0FvCobx6L_qhXi%2Bg3gA@mail.gmail.com> References: <547C5DD3.90604@rawbw.com> <20141201150225.GB64370@apollo.corbe.net> <547C88AD.40407@rawbw.com> <20141201153712.4304976.24709.1746@denninger.net> <CAMW5ToZh2oqry1TKma67MmiAHjMbUZmE%2B0POKHDaeP1cVQpoCw@mail.gmail.com> <CAJ-VmokGVnqeY6nm55q2Q83bTc_%2BKsq0FvCobx6L_qhXi%2Bg3gA@mail.gmail.com>
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Was there a specific reason why we couldn't just extend REUSEADDR/PORT to do this a la Linux? Just a simple round robin would make those useful perhaps On 01/12/2014 16:21, Adrian Chadd wrote: > Hi, > > I introduced a socket option in -HEAD that lets you bind multiple > things to the same listen ports. > > They're only load balanced if you're using RSS and set up RSS socket > options as well; otherwise only one gets the incoming requests. > > IP_BINDMULTI and IP6_BINDMULTI. > > > -a > > > On 1 December 2014 at 08:14, Someone Somewhere > <somewheresomeoneis@gmail.com> wrote: >> @Yuri , are you sure that the second instance of nc does not accept any >> connection? >> I did a simple test : -> >> #: nc -l 12345 (shell 1) >> #: nc localhost 12345 (shell2) >> at this point netstat shows that there is no one listening on 12345. This >> means any process should not be able to bind over port 12345(over TCP). >> # nc -l 12345 (shell 3, shell 1 , 2 still active) >> this instance of nc starts listening which I could verify via netstat cmd. >> # nc localhost 12345 (shell 4) >> this nc instance connected to the nc started in previous step over shell 3. >> >> Test ran on Fedora 20. >> [will try this on freeBSD VM if you confirm that this is what you are >> trying] >> >> >> Could you verify if your second nc(server) instance is listening on the >> same socket number? >> >> >> -Kunal. >> >> >> >> On 1 December 2014 at 21:07, Karl Denninger <karl@denninger.net> wrote: >> >>> The second bind() call does fail but if the application ignores the return >>> code.... Are you sure all the associated system call return codes are >>> being checked? >>> >>> The right way to do this Imho is to have a parent process that calls bind >>> and listen, gets the notification of an incoming connection via select() >>> (allowing detection of exceptions as well) and then calls accept() and, now >>> having a connected file handle, fork()s and executes whatever is to handle >>> the connection with the parent closing the handle so as to not orphan the >>> handle when the child exits. >>> >>> -- Karl >>> (On Passport PDA) >>> >>> >>> Original Message >>> From: Yuri >>> Sent: Monday, December 1, 2014 10:26 >>> To: Daniel Corbe >>> Cc: freebsd-net@freebsd.org >>> Subject: Re: Can multiple apps listen for TCP on the same port? >>> >>> On 12/01/2014 07:02, Daniel Corbe wrote: >>>> Generally the answer to your question is no. Two applications cannot >>>> occupy the same port on the same protocol at the same time. >>>> >>>> To expand on this answer and to hopefully shed some light on why the >>>> behavior you're observing with your application is absolutely correct; >>>> the calling application (in this case, nc) has to explicitly call bind(2) >>>> before it can begin accepting connections. If that port is already in >>>> use then the call to bind(2) will fail. And in your case I suspect nc >>>> is simply choosing to silently fail. >>> >>> Here the question is what does it mean "occupy the port"? The first >>> instance isn't listening any more. The listening socket was closed. Why >>> the presence of the socket that was accepted from (now closed) listening >>> socket in the first instance is considered "occupying it"? >>> >>> Actually no system call in the second instance ever fails. >>> >>> Yuri >>> _______________________________________________ >>> freebsd-net@freebsd.org mailing list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-net >>> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >>> >>> >>> %SPAMBLOCK-SYS: Matched [@freebsd.org+], message ok >>> >>> >>> _______________________________________________ >>> freebsd-net@freebsd.org mailing list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-net >>> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >>> >> _______________________________________________ >> freebsd-net@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-net >> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >
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