Unable to telnet to MariaDB container

Question

I'm using docker-compose to run MariaDB and it is working fine. I am fetching jasper server and maria DB docker images and running them. When I telnet the jasper server image, it responds correctly, but when I telnet to MariaDB, it says:

telnet localhost 3306
Trying ::1...
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused

What I might be doing wrong?
Here is the output of sudo docker ps -a:

CONTAINER ID        IMAGE                     COMMAND                  CREATED             STATUS              PORTS                                           NAMES
9e759f106006        bitnami/jasperreports:7   "/app-entrypoint.sh …"   21 minutes ago      Up 21 minutes       0.0.0.0:9093->8080/tcp, 0.0.0.0:443->8443/tcp   ceyedev_jasperreports_1
9242e52f6af8        bitnami/mariadb:10.3      "/opt/bitnami/script…"   21 minutes ago      Up 21 minutes       3306/tcp                                        ceyedev_mariadb_1

Here is my docker compose file:

version: '2'
services:
  mariadb:
    image: 'bitnami/mariadb:10.3'
    environment:
      - MARIADB_USER=bn_jasperreports
      - MARIADB_DATABASE=bitnami_jasperreports
      - ALLOW_EMPTY_PASSWORD=yes
    volumes:
      - 'mariadb_data:/bitnami'
  jasperreports:
    image: 'bitnami/jasperreports:7'
    environment:
      - MARIADB_HOST=mariadb
      - MARIADB_PORT_NUMBER=3306
      - JASPERREPORTS_DATABASE_USER=bn_jasperreports
      - JASPERREPORTS_DATABASE_NAME=bitnami_jasperreports
      - ALLOW_EMPTY_PASSWORD=yes
    ports:
      - '9093:8080'
      - '443:8443'
    volumes:
      - 'jasperreports_data:/bitnami'
    depends_on:
      - mariadb
volumes:
  mariadb_data:
    driver: local
  jasperreports_data:
    driver: local 

Answer 1

You have to open the ports in your Docker compose file (that thing you posted is called a Docker Compose file, not Dockerfile which is the one containing the commands to build a Docker image).

In the mariadb section make it like this:

services:
  mariadb:
    image: 'bitnami/mariadb:10.3'
    environment:
      - MARIADB_USER=bn_jasperreports
      - MARIADB_DATABASE=bitnami_jasperreports
      - ALLOW_EMPTY_PASSWORD=yes
    volumes:
      - 'mariadb_data:/bitnami'
    ports:
      - 3306

This way, the 3306 port of MariaDB will be exposed to your local computer. This means:

• that you may access MariaDB through the 3306 port
• that ANYONE with direct network access to your computer (i.e. local IP address) will be able to access MariaDB through port 3306.

Bear in mind those two things regarding your system security.