Docker compose (mysql, elasticsearch, kibana) with healthchecks

docker-compose.yml

version: '2.1'
services:
  mysql:
    container_name: mysql
    image: mysql:5.7
    ports:
      - "13306:3306"
    environment:
      - MYSQL_ROOT_PASSWORD=Welcome123
    healthcheck:
        test: ["CMD-SHELL", "mysqladmin -h 'localhost' -u root -pWelcome123 ping --silent"]
        interval: 30s
        timeout: 30s
        retries: 3
    volumes:
      - mysqldata:/var/lib/mysql
    networks:
      - dbnet

  elasticsearch:
    image: elasticsearch:5.3
    container_name: elasticsearch
    depends_on:
      mysql:
          condition: service_healthy
    healthcheck:
        test: ["CMD-SHELL", "curl --silent --fail localhost:9200/_cluster/health || exit 1"]
        interval: 30s
        timeout: 30s
        retries: 3
    environment:
      - "ES_JAVA_OPTS=-Xmx2g -Xms2g"
      - bootstrap.memory_local=true
      - cluster.name=adlp-cluster
    ports:
      - 19200:9200
      - 19300:9300
    volumes:
      - ./elasticsearch/config/elasticsearch.yml:/etc/elasticsearch/config/elasticsearch.yml
      - ./elasticsearch/config/jvm.options:/etc/elasticsearch/config/jvm.options
      - ./elasticsearch/config/log4j2.properties:/etc/elasticsearch/config/log4j2.properties
      - esdata:/usr/share/elasticsearch/data
    networks:
      - esnet
  kibana:
    image: kibana:5.3
    container_name: kibana
    depends_on:
      elasticsearch:
          condition: service_healthy
    ports:
     - "5601:5601"
    environment:
     - ELASTICSEARCH_URL=http://elasticsearch:9200
     - XPACK_MONITORING_ENABLED=false
    depends_on:
     - elasticsearch
    networks:
     - esnet

volumes:
  mysqldata:
    driver: local
  esdata:
    driver: local

networks:
  esnet:
    driver: bridge
  dbnet:
    driver: bridge

how does elasticsearch communicate with mysql? They are in 2 different networks. Shouldn't container elasticsearch belong to both esnet and dbnet?