I have a weird situation going on with an open network port. My main question is, why would there not be a program associated with an open TCP port:
netstat -ln --program Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:5666 0.0.0.0:* LISTEN -
For my specific case, there is supposed to be an nrpe daemon (opsview install) listening on port 5666, but there is no nrpe daemon running. If I try to start it, it exits immediately.
lsof -i :5666 doesn't show any output either. There is no (x)inetd running on my system.
Yes, I was running those commands as root. Telnet would could, but there was never any response.
After further investigation, I found a kernel error in
dmesg: this was an EC2 instance (actually several of them) running an older kernel (2.6.16 is apparently unstable). The fix to stop the crash was to upgrade kernels.
It looks like the way the kernel crashed caused the process to go away and leave the port open.