# 连接到特定服务器

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:

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

```java
// 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");
```

{% endtab %}

{% tab title="Java" %}

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

// Do something with the connection

nc.close();
```

{% endtab %}

{% tab title="JavaScript" %}

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

{% endtab %}

{% tab title="Python" %}

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

# Do something with the connection

await nc.close()
```

{% endtab %}

{% tab title="Ruby" %}

```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="C" %}

```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);
```

{% endtab %}
{% endtabs %}


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