ssh_exchange_identification: Coection closed by remote host

Sorry if already posted..
I am new to Linux and SSH..

I have installed ssh using " sudo apt-get install openssh-server"

Then i tried to login to another user account of same machine from root using ssh command

ssh user_name@ip_address

it is giving a single line error..

ssh_exchange_identification: Coection closed by remote host

Please help. I am stuck on this.