A recipe shows how you can attempt to connect to a TCP port using the nc command in every x seconds for n tries.
A typical server listens to a TCP port and can take some time to launch. We want to have a script that "ping" this TCP port to check that it is "alive" before starting a client to make the actual connection to the server.
This script is useful in Docker container orchestration when the launch of a client depends on the availability of TCP ports.
See source.