Two dockers

Network

docker network create pingpong

Ping service

cd ping
docker build -t ping-service .
docker run -it --rm --name ping-service-container --net pingpong -p 5000:5000 --entrypoint /bin/bash ping-service
python app.py

Pong service

cd ../pong
docker build -t pong-service .
docker run --rm --name pong-service-container --net pingpong -p 5001:5001 pong-service

Inspect network

docker network inspect pingpong

Browser

http://0.0.0.0:5000/ping