Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)

I am upgrading from 5.1.3 to 6.1.1 on CentOS 7
Its working perfectly in 5.1.3 but after running all the upgrades successfully its giving me the following error when I try to start seafile.sh

[08/04/17 16:00:25] …/common/session.c(132): using config file /home/seafile/conf/ccnet.conf
[08/04/17 16:00:25] …/common/ccnet-db.c(124): Failed to get database connection: Failed to connect to MySQL: Can’t connect to local MySQL server through socket ‘/tmp/mysql.sock’ (2).
failed to run “ccnet-server -t”

if i go back to 5.1.3 directory and start seafile and seahub. it works fine

can someone please help me fix this

Kind Regards