nats.docs/developing-with-nats/connecting/specific_server.md

Connecting to a Specific Server

The NATS client libraries can take a full URL, nats://demo.nats.io:4222, to specify a specific server host and port to connect to.

Libraries are removing the requirement for an explicit protocol and may allow nats://demo.nats.io:4222 or just demo.nats.io:4222. Check with your specific client library's documentation to see what URL formats are supported.

For example, to connect to the demo server with a URL you can use:

{% tabs %} {% tab title="Go" %}

// If connecting to the default port, the URL can be simplified
// to just the hostname/IP.
// That is, the connect below is equivalent to:
// nats.Connect("nats://demo.nats.io:4222")
nc, err := nats.Connect("demo.nats.io")
if err != nil {
    log.Fatal(err)
}
defer nc.Close()

// Do something with the connectioConnection nc = Nats.connect("nats://demo.nats.io:4222");

{% endtab %}

{% tab title="Java" %}

Connection nc = Nats.connect("nats://demo.nats.io:4222");

// Do something with the connection

nc.close();

{% endtab %}

{% tab title="JavaScript" %}

let nc = NATS.connect("nats://demo.nats.io:4222");
nc.on('connect', (c) => {
    // Do something with the connection
    doSomething();
    // When done close it
    nc.close();
});
nc.on('error', (err) => {
    failed(err);
});

{% endtab %}

{% tab title="Python" %}

nc = NATS()
await nc.connect(servers=["nats://demo.nats.io:4222"])

# Do something with the connection

await nc.close()

{% endtab %}

{% tab title="Ruby" %}

require 'nats/client'

NATS.start(servers: ["nats://demo.nats.io:4222"]) do |nc|
   # Do something with the connection

   # Close the connection
   nc.close
end

{% endtab %}

{% tab title="TypeScript" %}

// will throw an exception if connection fails
    let nc = await connect("nats://demo.nats.io:4222");
    // Do something with the connection

    // Close the connection
    nc.close();

{% endtab %} {% endtabs %}