[neural]

Ok, report back:

I checked up on selinux. Doesn't seem to be the issue. I've checked the audit.log files, could see nothing in there relating to calibre or the port.

I then went and temporarily disabled selinux, but no luck connecting, see below:

[root@localhost audit]# sestatus
SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   enforcing
Mode from config file:          enforcing
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Max kernel policy version:      31
[root@localhost audit]# setenforce 0
[root@localhost audit]# sestatus
SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   permissive
Mode from config file:          enforcing
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Max kernel policy version:      31
[root@localhost audit]# echo 0 > /s
sbin/ srv/  sys/

This has now truly flummoxed me...