Hi Victor, On Thu, Aug 20, 2020 at 12:09:03PM +0700, Victor Sudakov wrote: > There is a process listening on 127.0.0.1:8081 but for some reason > netstat/sockstat/ss do not show it listening on IPv4. Is this a bug or a > feature?
I think it's listening on an IPv4-mapped IPv6 address so it can accept either v4 or v6. Does this answer your question? https://unix.stackexchange.com/questions/152612/netstat-why-are-ipv4-daemons-listening-to-ports-listed-only-in-a-inet6 Daemons that want to receive connections will do the equivalent of: bind(address, port) The address will determine the interface and whether it is v4 or v6 or whatever. If they instead do: bind(INADDR_ANY, port) then this will bind to every interface whether it's v4 or v6 and the daemon will get udp6 or tcp6 sockets that can from fromn/to a v4 address. If you daemon instead had an explicit list of address/port pairs to listen on then it would do multiple binds and I believe the IPv4 ones would show up in netstat etc as being tcp4. Cheers, Andy -- https://bitfolk.com/ -- No-nonsense VPS hosting