How to connect docker service of emqx

I've set up a service which is used for mqtt connecting of IoT devices, thus the devices can connect to the emqx service;
But I found there's no approach of connecting to 1883 port which is used for MQTT over TCP listener, neither domain or ip can be used for connecting;So i got confused about this in the doc:

So is there any workable setup of mqtt docker service that provides ingress? or I have to separate a standalone mqtt service in another server that not locate in medstack?