Docker error connecting to host mysql

Docker version 17.03.1-ce, build c6d412e OS: Ubuntu

I am trying to connect to host mysql from the docker container. but i am getting this error.

Error: connect ECONNREFUSED 0.0.0.0:3306

I am getting same for mysql if i use mysql container. Tried 127.0.0.1 and localhost also.

version: '2'

services:

### Applications Code Container 
#############################

  applications:
    image: tianon/true
    volumes:
      - ${APPLICATION}:/var/www/html

  apache2:
    build:
      context: ./apache2
    volumes_from:
      - applications
    volumes:
      - ${APACHE_HOST_LOG_PATH}:/var/log/apache2
      - ./apache2/sites:/etc/apache2/sites-available
    ports:
      - "${APACHE_HOST_HTTP_PORT}:80"
      - "${APACHE_HOST_HTTPS_PORT}:443"
    networks:
      - frontend
      - backend

  node:
    build:
      context: ./node
    volumes_from:
      - applications
    ports:
      - "4000:30001"
    networks:
      - frontend
      - backend    


### MySQL Container  #########################################

  mysql:
    build:
      context: ./mysql
    environment:
      - MYSQL_DATABASE=${MYSQL_DATABASE}
      - MYSQL_USER=${MYSQL_USER}
      - MYSQL_PASSWORD=${MYSQL_PASSWORD}
      - MYSQL_ROOT_PASSWORD=${MYSQL_ROOT_PASSWORD}
    volumes_from:
      - applications  
    volumes:
      - ${DATA_SAVE_PATH}/mysql:/var/lib/mysql
      - ./mysql/docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d
    ports:
      - "${MYSQL_PORT}:3306"
    networks:
      - backend


### Networks Setup ############################################

networks:
  frontend:
    driver: "bridge"
  backend:
    driver: "bridge"

### Volumes Setup #############################################

volumes:
  mysql:
    driver: "local"
  mongo:
    driver: "local"
  node:
    driver: "local"
  apache2:
    driver: "local"