Netstat Issue – Netstat Shows a Listening Port with No PID but lsof Does Not

netstatportrpc

This question is similar to Network port open, but no process attached?

I've tried everything from there, reviewed the logs, etc… and can't find anything.

My netstat shows a TCP listening port and a UDP port without a pid. When I search lsof for those ports nothing comes up.

netstat -lntup
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:44231           0.0.0.0:*               LISTEN      -               
udp        0      0 0.0.0.0:55234           0.0.0.0:*                           -

The following commands display nothing:

lsof | grep 44231
lsof | greo 55234
fuser -n tcp 44231
fuser -n udp 55234

After rebooting, those "same" two connections are there except with new port numbers:

netstat -lntup
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:45082           0.0.0.0:*               LISTEN      -               
udp        0      0 0.0.0.0:37398           0.0.0.0:*                           -

And once again, the lsof and fuser commands show nothing.

Any ideas what they are? Should I be concerned about them?

Best Answer

From data you provided I'd say it's related to some NFS mounts or something using RPC.

you can check with rpcinfo -p for ports that might be used by some of RPC related services.

Here is how it looks on my system

# netstat -nlp | awk '{if ($NF == "-")print $0}'
tcp        0      0 0.0.0.0:55349           0.0.0.0:*               LISTEN      -               
udp        0      0 0.0.0.0:18049           0.0.0.0:*                           - 

# rpcinfo -p
   program vers proto   port
    100000    2   tcp    111  portmapper
    100000    2   udp    111  portmapper
    100024    1   udp  10249  status
    100024    1   tcp  10249  status
    100021    1   udp  18049  nlockmgr
    100021    3   udp  18049  nlockmgr
    100021    4   udp  18049  nlockmgr
    100021    1   tcp  55349  nlockmgr
    100021    3   tcp  55349  nlockmgr
    100021    4   tcp  55349  nlockmgr
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