Available ports on a data node?

Elastic Stack Elasticsearch
1

What ports / access need to be open on a data node for it to join a cluster?

Im attempting to join a data node to a master but am getting timeouts. From the data node I can get the 'all is well' curl response from port 9200 but the join doesn't seem to work.

From the master node I don't know what to probe on the data node to look for blocks.

2

Could you please provide elasticsearch.log on master and data node?

3

Elasticsearch nodes communicate internally on the 9300 port so that has to be open.