Can I bind to a specific host? How is the host option passed through?

Question

RepoPilot · Accepted Answer

Yes, you can bind to a specific host using the `host` option in the options object passed to `getPort()`.

According to the API documentation in [readme.md:L80-L87], the `host` option is:

> Type: `string`
> 
> The host on which port resolution should be performed. Can be either an IPv4 or IPv6 address.
> 
> By default, it checks availability on all local addresses defined in [OS network interfaces](https://nodejs.org/api/os.html#os_os_networkinterfaces). If this option is set, it will only check the given host.

The `host` option is passed through to the underlying port checking mechanism. In [index.js:L61-L78], the `getAvailablePort` function handles this:

```javascript
const getAvailablePort = async (options, hosts) => {
	if (options.host || options.port === 0) {
		return checkAvailablePort(options);
	}
	// ... checks all hosts if no host specified
};
```

When you specify a `host`, it directly calls `checkAvailablePort(options)` which then passes the options to `server.listen()` [index.js:L47-L60]. The options object (including the `host` property) is passed directly to Node's `net.createServer().listen()` method, which uses the host to bind to that specific address.

For example, you can call:
```js
await getPort({host: '127.0.0.1', port: 3000});
```

This will check if port 3000 is available specifically on the 127.0.0.1 address.

FOLLOW_UPS:
- What happens when host option is not specified?
- How does the exclude option work with host?
- Can I use IPv6 addresses with the host option?