OpenSSH is a freely available version of the Secure Shell (SSH) protocol family of tools for remotely controlling a computer or transferring files between computers.
If the openssh-server not installed yet, you will get error : openssh connection refused.
It is not about firewall disable.
When you cannot remote to the other PC or server in the network, just install OpenSSH-server. Use the command line below
sudo apt-get install openssh-server
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Good luck! Have a nice day.
