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 demo.nats.io:4222 or just demo.nats.io. In the later example the default port 4222 will be used. 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:

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

Java

// Connection is AutoCloseable
try (Connection nc = Nats.connect("nats://demo.nats.io:4222")) {
    // Do something with the connection
}

JavaScript

const nc = await connect({ servers: "demo.nats.io" });
// Do something with the connection
doSomething();
await nc.close();

Python

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

# Do something with the connection

await nc.close()

C#

// dotnet add package NATS.Net
using NATS.Net;

await using var client = new NatsClient("nats://demo.nats.io:4222");

// It's optional to call ConnectAsync()
// as it will be called when needed automatically
await client.ConnectAsync();

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

C

natsConnection      *conn = NULL;
natsStatus          s;

// If connecting to the default port, the URL can be simplified
// to just the hostname/IP.
// That is, the connect below is equivalent to:
// natsConnection_ConnectTo(&conn, "nats://demo.nats.io:4222");
s = natsConnection_ConnectTo(&conn, "demo.nats.io");
if (s != NATS_OK)
  // handle error

// Destroy connection, no-op if conn is NULL.
natsConnection_Destroy(conn);