Docker network allows multiple Docker containers to communicate with each other

With Docker network, a client application in another Docker container can access service in the server container. 

First, create a Docker network:

docker network create my-custom-net

Then, when you are creating and starting the server and the client containers, use the --network option to put them on network you created. For example:

docker run --name=mysql1 --network=my-custom-net -d mysql/mysql-server

docker run --name=myapp1 --network=my-custom-net -d myapp

The myapp1 container can then connect to the mysql1 container with the mysql1 hostname and vice versa, as Docker automatically sets up a DNS for the given container names. In the following example, we run the mysql client from inside the myapp1 container to connect to host mysql1 in its own container:

docker exec -it myapp1 mysql --host=mysql1 --user=myuser --password