Can docker not be accessed externally without setting port mapping

  docker, question

In the milletopen-falconOne of the parts is fromdockerI got it back.
Following the tutorial, docker’s:

# make the imageļ¼Œrun commands under dir of dashboard:
 docker build -t falcon-dashboard:v1.0 .
 # start the container
 docker run -itd --name aaa --net host \
 -e API_ADDR= \
 -e PORTAL_DB_PORT=3306 \
 -e PORTAL_DB_USER=root \
 -e PORTAL_DB_PASS=123456 \
 -e PORTAL_DB_NAME=falcon_portal \
 -e ALARM_DB_PASS=123456 \
 -e ALARM_DB_PORT=3306 \
 -e ALARM_DB_USER=root \
 -e ALARM_DB_PASS=123456 \
 -e ALARM_DB_NAME=alarms \

From the above command, I don’t see what -p is used to bind the port mapping, but somehow, I can still request the port of an item in the container docker.
This is strange.

--netOption has been set for docker’s network, seenetwork settings
Network can customize the network and docker connected to the same network can communicate with each other.