Suppose your machine IP is 192.160.xx.xx ,   docker container ip as 172.10.xx.xx.

Let us consider your case where you expose 80 port of your container...  it will like
172.10.xx.xx:80 pointing 192.160.xx.xx:<some random port>

This happens only when you provide to publish all port, instead if you know the number of webapps your going to use,   then you can dedicate your system port to 80 port of a container webapp(publish the port yourself)
(docker run -p imagename) ip:hostPort:containerPort
1st container 172.10.xx.2:80 to 192.160.xx.xx:5000
2nd container 172.10.xx.3:80 to 192.160.xx.xx:6000
3rd container 172.10.xx.4:80 to 192.160.xx.xx:7000

So the IP will be your machine IP and the port is fixed separate webapps.  

Hope this helps

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