Can connect to Elasticsearch 5 remotely but not locally - linux

Question

I recently upgraded from Elasticsearch 1.5 to Elasticsearch 5.5, and I can connect fine remotely, but not from localhost.
I updated elasticsearch.yml to be able to connect remotely:
network.host: 0.0.0.0
And the elasticsearch logs look fine to me:
[2017-11-05T22:44:23,441][INFO ][o.e.n.Node ] [node1] starting ...
[2017-11-05T22:44:23,655][INFO ][o.e.t.TransportService ] [node1] publish_address {[ip address]:9300}, bound_addresses {127.0.0.1:9300}, {[::1]:9300}, {[ip address]:9300}
[2017-11-05T22:44:23,666][INFO ][o.e.b.BootstrapChecks ] [node1] bound or publishing to a non-loopback or non-link-local address, enforcing bootstrap checks
[2017-11-05T22:44:26,712][INFO ][o.e.c.s.ClusterService ] [node1] new_master {node1}{s-J7aStjQFuwor-WY6bSCQ}{nv4GVIQ6SwScPiebRHBQBQ}{localhost}{[ip address]:9300}, reason: zen-disco-elected-as-master ([0] nodes joined)
[2017-11-05T22:44:26,733][INFO ][o.e.h.n.Netty4HttpServerTransport] [node1] publish_address {[ip address]:9200}, bound_addresses {127.0.0.1:9200}, {[::1]:9200}, {[ip address]:9200}
[2017-11-05T22:44:26,734][INFO ][o.e.n.Node ] [node1] started
I am wondering if it is related to the proxy, since when I try run curl localhost:9200, I get the following:
...
<p>The following error was encountered while trying to retrieve the URL: http://localhost:9200/</p>
<blockquote id="error">
<p><b>Connection to 127.0.0.1 failed.</b></p>
</blockquote>
<p id="sysmsg">The system returned: <i>(111) Connection refused</i></p>
<p>The remote host or network may be down. Please try the request again.</p>
...
Any ideas or tips on how to narrow down the issue would be helpful.

Answer 1

It turned out a http_proxy bash variable was set which was proxying all outbound traffic. Once this variable was unset, the curl command worked.
It also turned out that before this fix was made, I realized our Java applications were still able to connect to Elasticsearch locally, it was just the curl command that wasn't working.