"connect to address x.x.x.x port nnnnn Connection refused"

Question

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.

Answer 1

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)