Chris, David, Dmitry thanks for your valuable input. This helps me a lot.
Best regards Christoph > -----Original Message----- > From: Chris Hegarty [mailto:chris.hega...@oracle.com] > Sent: Donnerstag, 14. Juli 2016 12:31 > To: Langer, Christoph <christoph.lan...@sap.com> > Cc: net-dev@openjdk.java.net; nio-...@openjdk.java.net > Subject: Re: Help needed: Java Socket and close detection > > Some further reading... > > https://docs.oracle.com/javase/8/docs/technotes/guides/net/articles/connectio > n_release.html > > -Chris. > > > On 13 Jul 2016, at 21:37, Dmitry Samersoff <dmitry.samers...@oracle.com> > wrote: > > > > Christoph, > > > > My $0.2 > > > > Typically you see RST packet when the data come to a *closed* socket. > > You shouldn't get RST if client/server communication shutdown properly. > > > > Also balancer may take a care about connection shutdown (it needs to > > update internal tables) so it's possible that you never get RST after > > balancer. > > > > Moreover, there are RST based attack and scanning methods so firewall > > might be set to reject RST packets and doesn't pass it to inside network. > > > > I.e. IMHO, customer server should be updated to live without RST. > > > > -Dmitry > > > > On 2016-07-13 18:29, Langer, Christoph wrote: > >> Hi folks, > >> > >> > >> > >> I have a question to the experts - regarding an issue that was reported > >> to me by a customer. > >> > >> > >> > >> In the customer scenario they are running a Servlet engine and the > >> Servlet is constantly sending data to a browser client. When the browser > >> client is closed, the server does not get a notification of the other > >> end having been terminated and is constantly sending out data and > >> blocking an application thread. I'm under the assumption that the server > >> should get an RST packet from the network upon writing/flushing data to > >> the OutputStream as soon as the client is gone and hence an Exception > >> should pop up but this isn't happening. > >> > >> > >> > >> There is a load balancer and maybe other network infrastructure involved > >> in between the Servlet JVM and the browser client. We did some TCPDUMP > >> tracing at the load balancer and we could not see an RST packet coming > >> in from the client side. But when I'm running the scenario without all > >> this network infrastructure involved, e.g. between servers and clients > >> in the same network, I would always observe an RST packet once I close > >> the browser. A FIN packet is received, too, but this does not lead to an > >> Exception and to all my knowledge this can't be detected, not from the > >> java Socket API and even less from the Servlet API which is just dealing > >> with Streams. > >> > >> > >> > >> So my question to the experts is most of all: Would you agree that an > >> RST packet should be generated in the network and received by the > >> server? Or is it a normal behavior that servers must deal with not > >> receiving RSTs and hence needing to wait for a timeout until e.g. the > >> load balancer generates an RST? Also, is there any way to detect a FIN > >> in the JVM and react on it? > >> > >> > >> > >> Thanks in advance and best regards > >> > >> Christoph > >> > >> > >> > > > > > > -- > > Dmitry Samersoff > > Oracle Java development team, Saint Petersburg, Russia > > * I would love to change the world, but they won't give me the sources.
