wait_for_hosts.sh

#!/bin/sh

wait_for_hosts () {
  for host in $@; do
    while ! timeout 5 bash -c "echo > /dev/tcp/${host//:/\/}"; do
      echo "$host is not available. Retrying..."
      sleep 2
    done
    echo $host is available!
  done
}

WAIT_FOR_HOSTS="google.com:80 google.de:80 bing.com:443"
wait_for_hosts $WAIT_FOR_HOSTS

wait_for_hosts google.com:80 google.de:80 bing.com:443