ssh_exchange_identification: Connection closed by remote host

Solution 1:

Check to see if the IP you are connecting from is showing up in /etc/hosts.deny on the remote server, and also check to see if you have lots of failed login attempts in /var/log/secure. If you do, delete those entries out of both files and you can sometime get back in.

Solution 2:

sh_exchange_identification: Connection closed by remote host even if the key is correct

Login via console or try login multiple times in ssh

Then check the permission of /var/log/btmp it must be 600 chmod 600 /var/log/btmp

Solution 3:

Also, try logging in without using your private key. the only way i know to do this is to temporarily move aside your private key file.