Solving a “communications link failure” with JDBC and MySQL [duplicate]

Answer 1

In case you are having problem with a set of Docker containers, then make sure that you do not only EXPOSE the port 3306, but as well map the port from outside the container -p 3306:3306. For docker-compose.yml:

version: '2'

services:
    mdb:
        image: mariadb:10.1
        ports:
            - "3306:3306"
        …