RDS Laravel SQLSTATE[HY000] [2002] Connection refused

I am trying to connect my Laravel 5.1 application using rds mysql. But it ended up in getting

SQLSTATE[HY000] [2002] Connection refused

The same rds database is using in other EC2 instance. But it works fine there. Only difference between two EC2 is the security group. As i come to notice that 3306 port should be open for mysql. I make it open in my security group. But still getting the same error. Can anybody help me to resolve this issue?

Thanks in advance for any help

via Chebli Mohamed