Port 9300 on Elasticsearch
elasticsearch
Solution
Elasticsearch will bind to a single port for both HTTP and the node/transport APIs.
It'll try the lowest available port first, and if it is already taken, try the next. If you run a single node on your machine, it'll only bind to 9200 and 9300.
See also: Elasticsearch Internals: Networking Introduction
Problem
According to the documentation, Elasticsearch reserves port 9300-9400 for cluster communication and port 9200-9300 for accessing the elasticsearch APIs. You get the impression that these ranges are inclusive: so port 9300 is part of the first and the second port range. Now, my IT ops department won't like that, so hopefully I got it wrong. Anyone knows?