I always appreciate your depth of knowledge, Chris. "hand-wavy device supporting NIO for Java"
Could you write us a quick paragraph expanding on this idea? I'm happy to follow a pointer to a well written article (something up to your standards). On 3/31/20, Christopher Schultz <ch...@christopherschultz.net> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA256 > > Frank, > > On 3/31/20 09:30, Frank Tornack wrote: >> Yes, these too are for communication between processes. Only you >> don't use the network stack. This is a special feature of Unix-like >> operating systems. >> >> DGRAM, unlike STREAM, does not know connection states. Therefore >> STREAM is comparable to a local TCP connection. Unix domain sockets >> exist in the file tree as special files. Access is controlled by >> file permissions, as is usual for files. > > Yup. It's helpful to see the column headers for your netstat output, > André: > >> Proto RefCnt Flags Type State I-Node >> PID/Program name Path unix 2 [ ] STREAM >> CONNECTED 167427210 27514/java unix 2 [ ] STREAM >> CONNECTED 167423436 27514/java > > Each "unix" protocol-connection (UNIX domain socket) has an associated > inode on the root filesystem, but no path. Basically, it's magic. :) > > The nice thing on *NIX is that even though there is a hand-wavy device > supporting NIO for Java, it doesn't consume pairs of ports (which are > a limited resource; see our recent discussion on the limits of TCP > port numbers). > > - -chris > >> Am Dienstag, den 31.03.2020, 14:29 +0200 schrieb André Warnier >> (tomcat/perl): >>> On 31.03.2020 14:20, Mark Thomas wrote: >>>> On 31/03/2020 11:20, Aditya Kumar wrote: >>>>> Tomcat 9.0.30 on Windows Server 2012 / Java 1.8 >>>>> >>>>> I've noticed on a freshly installed version of tomcat 9, >>>>> upon startup there are several connections to and from >>>>> localhost on different ports >>>>> >>>>> For example on my tomcat server there are 4 connections to >>>>> and from localhost (output from netstat) >>>>> >>>>> >>>>> TCP 0.0.0.0:8080 0.0.0.0:0 >>>>> LISTENING 3972 >>>>> >>>>> TCP 127.0.0.1:55618 127.0.0.1:55619 >>>>> ESTABLISHED 3972 >>>>> >>>>> TCP 127.0.0.1:55619 127.0.0.1:55618 >>>>> ESTABLISHED 3972 >>>>> >>>>> TCP 127.0.0.1:55620 127.0.0.1:55621 >>>>> ESTABLISHED 3972 >>>>> >>>>> TCP 127.0.0.1:55621 127.0.0.1:55620 >>>>> ESTABLISHED 3972 >>>>> >>>>> TCP [::]:8080 [::]:0 >>>>> LISTENING 3972 >>>>> >>>>> These can grow to a large number (several thousand) on a >>>>> busy system. What are these connections used for? What caused >>>>> them? What thread are they attributed to? >>>> >>>> The Java NIO implementation on Windows uses TCP for >>>> intra-process signalling. It opens a pair of self-connected >>>> sockets for every Selector. >>>> >>>> Mark >>>> >>> >>> While we're at it, under Linux, are the following for a similar >>> reason ? >>> >>> output of : netstat -pan | grep 27514 (tomcat's JVM PID = >>> 27514) [...] unix 2 [ ] STREAM CONNECTED >>> 167427210 27514/java unix 2 [ ] STREAM >>> CONNECTED 167423436 27514/java >>> >>> >>> >>> --------------------------------------------------------------------- >>> >>> > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org >>> For additional commands, e-mail: users-h...@tomcat.apache.org >>> >> >> >> --------------------------------------------------------------------- >> >> > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org >> For additional commands, e-mail: users-h...@tomcat.apache.org >> > -----BEGIN PGP SIGNATURE----- > Comment: Using GnuPG with Thunderbird - https://www.enigmail.net/ > > iQIzBAEBCAAdFiEEMmKgYcQvxMe7tcJcHPApP6U8pFgFAl6DUP8ACgkQHPApP6U8 > pFgxiBAAkmLWWhwvrLW+RJ5j3ZKEu5cXQ0x3/zsMpFuP2GPok1lemXixa8T91lSO > eGg6W80DhVb76tDJl4Akt3L8ejN2XNgSxnHgGfEiCvTughYryAmHNXxze3ZMj4BQ > pvIO8hCc1nSlti71h6C2vEGYLnwkHyMulIolYaHP+SxKX7PSxXcfo4zD6vvpTvnO > U5Hrk7H8JjXCANrd8LsChN8w8AkWMUJpu/TUXFYy8bWEN9Ui7SdGqfa1t+pwnl8+ > JZqO1moBP9WcMA/XR1msWIbkA8B1r+ICWqlqcdGlvkXrHzkiALdqpxy0WiKAs1Tn > J+uPp0mAGpXRU3NGibr5NMtHLQ3Kl+X821yHYjF0XjqFwjLgvQNrmdYwblqFCUPB > 9sIVr6CuWAxPM61QZ9Bi9fT4MrIA6f8iSEa7BDJmUWhARPQMKn6fjIOMd8Cok882 > cGU1WT8O2SrtQV+y7wJbbq4aP4e6vRi/nSqI2hlSFdTBfD1Grj+t5JPHg35AafR4 > +6qum9rVF3AKf47UoJFrXG9smWLkUVVsJuZbdHLofmQEV0ovOMzAPx2GR9oSR2/M > sCxdUdqrhEW08wwYwIOV59vNa9pn/X/SOEre09yLH/GMV3H03CiQni616luWPrQt > 0BzFi4+8TPVzKCaq88ThyjJnEMuDU9RNeS7IHScHTXQa6rflB7E= > =q/Fd > -----END PGP SIGNATURE----- > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
