Issue when connecting to the Couchbase server

We recently deployed a Couchbase server onto a Linux server and tried connecting our PHP code to it. However, we kept on getting Error Code:16, network failure. We tried connecting to it from different server in network and from its own server itself - but same issue.

If we access the CB front-end at http://{Server Public IP}/index.html - the front-end works. So, we know the server is up. We just have issue when we try to use our own PHP code to connect to it.

On development machine running on Windows - we didn’t encoutner this error.

Can anyone provide any info what possible setting did we miss?

Error encountered
Error code: 16
Error message: Network failure

<–simple code that we used to connect to the server–>
try {
$cb = new Couchbase(“”);
echo $cb->getResultMessage();
} catch (CouchbaseException $e) {