https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-elasticsearch-on-ubuntu-20-04
To test:
Run from the local server to see if the server can connect to the elasticsearch cluster:
curl -X GET 'http://localhost:9200'
Run a test from a remote server, to see if a remote user can access the cluster
curl -X GET 'http://XXXXXX:9200'