A NATS system is usually identified by a standard URL with the nats or tls protocol, e.g. nats://demo.nats.io. A NATS system can be a single server, a small cluster or a global super cluster. Throughout these examples we will rely on a single test server, provided by nats.io, at nats://demo.nats.io, where 4222 is the default port for NATS.

NATS also supports secure connectivity using TLS via the tls protocol. Most clients support auto-detection of a secure connection using the URL protocol tls. There is also a demo server running TLS at tls://demo.nats.io:4443. The protocol requirement is being made optional for many client libraries, so that you can use demo.nats.io:4222 as the URL and let the client and server resolve whether or not TLS is required.

There are numerous options for a NATS connection ranging from timeouts to reconnect settings.