Installing and configuring OpenSSH (SSHD) server on Linux/Ubuntu

Go to Terminail (Shortcut -> ctrl + alt +t) and type the following command
 

sudo apt-get install openssh-server openssh-client

This ssh is required when suppose you are trying to ssh to localhost or from one machine to other machine and connection refused error comes, so you need to install sshd server to be able to connect to the other machind :)