I've been trying to get elastic search (running behind a vpn) to listen to incoming requests from other machines on port 9200 using ipv4. Without modifying the default elasticsearch.yml, I ran netstat and received:
tcp6 0 0 127.0.0.1:9200 :::* LISTEN 8079/java
tcp6 0 0 ::1:9200 :::* LISTEN 8079/java
tcp6 0 0 127.0.0.1:9300 :::* LISTEN 8079/java
tcp6 0 0 ::1:9300 :::* LISTEN 8079/java
With the default settings, I could curl elastic search fine from inside the machine, but could not connect curl it from outside using curl -XGET [IP]:9200 (curl: (7) Failed to connect to [IP] port 9200: Connection refused)
I set network.host: 0.0.0.0, stopped and started elastic search sudo systemctl start elasticsearch.service and waited for a minute or two, but nothing was listening on 0.0.0.0:9200. I've also tried _local_:ipv4 and 0.0.0.0:ipv4 with no luck.
I added -Djava.net.preferIPv4Stack=true to jvm.options and now I am getting (with # network.port commented out):
tcp 0 0 127.0.0.1:9200 0.0.0.0:* LISTEN 11131/java
tcp 0 0 127.0.0.1:9300 0.0.0.0:* LISTEN 11131/java
I tried to set network.host: 0.0.0.0 again and restart the service but now I don't see it listening to any ports.
In the log files I receive an error [1]: the default discovery settings are unsuitable for production use; at least one of [discovery.seed_hosts, discovery.seed_providers, cluster.initial_master_nodes] must be configured
Setting cluster.initial_master_nodes: node-1 fixed it. Works.