Hi Jens, Have you tested whether your server is able to accept concurrent connections normally? E.g. if you open a connection with telnet or something without sending any bytes, leave that open, and then try to use your server, does it work?
What does your listen loop look like? -Kenton On Tue, Nov 8, 2022 at 1:33 PM Jens Alfke <j...@mooseyard.com> wrote: > I’ve got a CapnP-based server program running on a Raspberry Pi 4. It’s > written in C++, using CapnP 0.9.1. It’s single-threaded; the main() > function just sets up a listener, calls kj::NEVER_DONE.wait, and stays > there. > > It works fine, except that every few weeks it stops accepting connections; > it either doesn’t accept the incoming socket at all or never reads from it, > I can’t tell which; all I see is that the client times out and gives up > after 15 seconds. Then I have to kill and relaunch the server, after which > it works fine again for a while. > > The server process itself isn’t hung; it’s in epoll waiting for events. I > attached gdb and got this backtrace: > > #0 0xb6b8563c in epoll_wait (epfd=7, events=0xbecb4210, maxevents=16, > timeout=-1) > #1 0x0052edcc in kj::UnixEventPort::doEpollWait (this=0x1fed420, > timeout=-1) > #2 0x0052e58c in kj::UnixEventPort::wait (this=0x1fed420) > #3 0x00487744 in kj::EventLoop::wait (this=0x1fed4e0) > #4 0x00488460 in kj::_::waitImpl (node=..., result=..., waitScope=…) > #5 0x00488bd8 in kj::_::NeverDone::wait (this=0x72d3c0 <kj::NEVER_DONE>, > waitScope=…) > … > > > The last line in the log shows that it received a connection from some > unknown IPv4 address which geolocates to Russia (this happens a few times a > day; the server’s on my home LAN but exposes a public port and I assume > these are random hackers looking for vulns.) This connection never did > anything, not surprisingly since I doubt hackers are expecting anything > other than HTTP, but the logs show the socket never closed. And sure > enough, if I run `lsof` I see an open TCP port from that address. (Which > has been open for at least 24 hours, strangely; doesn’t the disconnect idle > TCP connections after 90 minutes?) > > I’m not sure what to do about this. I assume CapnP is capable of handling > multiple incoming connections, so this idle socket won’t block others from > connecting, right? But if not, then why isn’t it accepting any connections? > > —Jens > > -- > You received this message because you are subscribed to the Google Groups > "Cap'n Proto" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to capnproto+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/capnproto/008DEC56-3B4D-4CF7-BFC3-5BECC13BE502%40mooseyard.com > <https://groups.google.com/d/msgid/capnproto/008DEC56-3B4D-4CF7-BFC3-5BECC13BE502%40mooseyard.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Cap'n Proto" group. To unsubscribe from this group and stop receiving emails from it, send an email to capnproto+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/capnproto/CAJouXQ%3D6xH_pyvRGBnRpTma6_K2mU8Ogn%2BptcQ9RytARhAUrAw%40mail.gmail.com.
