When I ssh ( Openssh (7.2p2 ) to (Ubuntu 16.04) server from the (Ubuntu 18.04) workstation for the first time I get the following message "connect to address x.x.x.x port nnnnn Connection refused" (port 22 is not being used ) and ufw has been set to allow the port number being used.
Make sure your
sshd.service is running:
$ systemctl status sshd
If it is not running, run it:
$ sudo systemctl start sshd
Connection refused could be because of the service is not running, the port is wrong or firewall could block it.
You could allow ssh by the next command:
$ sudo ufw allow ssh
Check if your service is actually running on specified port (replace 22 to your own specified port):
$ sudo lsof -i -n -P | grep "22 " cupsd 791 root 7u IPv4 27822 0t0 TCP 127.0.0.1:631 (LISTEN) sshd 10927 root 3u IPv4 135947 0t0 TCP *:22 (LISTEN) sshd 10927 root 4u IPv6 135949 0t0 TCP *:22 (LISTEN)
Check if you could connect to localhost first:
$ ssh user@localhost -p 22 Welcome to Ubuntu 20.04 LTS (GNU/Linux 5.4.0-29-generic x86_64)