MySQL - com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

While connecting to My SQL database, I got following error message:

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

I had personal firewall software running, which was blocking default TCP port which MY SQL clients used to connect to the database server. When I opened TCP port 3606, I managed to resolve the Communications link failure problem.