nc reporting "nc: Address already in use" but no port assignment in ss, netstat, lsof or fuser

English Network/Internet
#1

Command: nc -l IP_ADDRESS 50000
returns: nc: Address already in use

But when I am searching what application is using that port, I got nothing. I was using netstat, ss, tcpdump, fuser, lsof and no output for that port.
Kernel version: 5.3.18-150300.59.98-default
Sles version 15.3

issue very similar to that thread: https://serverfault.com/questions/311009/netstat-shows-a-listening-port-with-no-pid-but-lsof-does-not/847910#847910; but I am not getting anything specific with netstat command.

Wanted to check that with u guys, before I will engage SUSE support

L.

#2

Hi and welcome to the Forum :slight_smile:
For SUSE products the place to visit is https://community.suse.com/

The ss command on the host in question should show user/pid info


ss -tup
#3

As mentioned, “ss -tup | grep 50000” giving me no output.

L

#4

As mentioned, “ss -tup | grep 50000” giving me no output.
The same for netstat, lsof and fuser. No output when searching for something with that port

The ss command on the host in question should show user/pid info


ss -tup

[/QUOTE]

#5

Hi
On the host in question? If so then what ever was connected isn’t now to the service/application running and allocating that port range…

#6

Don’t know. Those are dynamic ports, so maybe at some point in time there was application running on that port. But what that changing?
Or maybe there is a way to check that?