Cant reach elasticsearch

I have 2 questions :

I have installed ELK on a different machine and am able to reach kibana but not elasticsearch. When I ping I see http://:9200/ "mmm...can’t reach this page" as if the address is incorrect.

When logstash started I see its started with /bin/java -Xms1g -Xmx1g where can I change those params ?

Kindly suggest.

network not use localhost 9200

Cant understand.

Did you config a valid network IP in elasticsearch.yml ?

It read like node.name: ${HOSTNAME} in that config file.

If you access "http://<your_external_server_ip>:9200" in the browser gives some error ?

You can change the jvm size on jvm.options file in the elasticsearch configuration directory.