[Nut-upsuser] NUT Client Not Working, Server OK

Manuel Wolfshant wolfy at nobugconsulting.ro
Wed Feb 16 23:29:08 GMT 2022

On 2/16/22 17:06, William Cole via Nut-upsuser wrote:
> Hello All,
> I ran telnet on both machines:
>    First from the server [235] to the client [236]
>    Then from the client [236] to the server [235]
> The result in both cases:
>    Trying 192.168.1.xxx
>    telnet: Unable to connect to remote host: Connection refused.
I am 90% sure that you have a firewall that blocks TCP connections. Many 
modern linux distros come with a default firewall which blocks all 
incoming connections or allow a very limited subset of ports, like ssh  
( port 22 ) and web ( port 80 and/or 443 ).

You can do a quick test by running as root ( or via sudo if needed ) one 
of the following two commands on the server machine:

     iptables -I INPUT -p tcp --dport 3493 -j ACCEPT <==  this will 
enable access to port TCP/3493


     iptables -F <=== this should disable the firewall completely. Note 
that depending on the distribution that you use, a more civilized way to 
( temporary ) disable the firewall exists, for instance in recent 
Debian/Ubuntu you'd run /ufw disable/ while on CentOS/RHEL you'd use 
/systemctl stop firewalld ( /with the obvious /ufw enable/ resp 
/systemctl start firewalld/ to enable the firewall back )

If I am right, once you've allowed the incoming connection, repeating 
the telnet command should succeed. In this case you must modify the 
firewall and add a permanent rule to allow the connection.


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