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

Yes, you can bind to a specific host using the host option. Here's how it works:

The host Option

The host option is part of the Options type [index.d.ts:L3-L65] and allows you to specify either an IPv4 or IPv6 address for port resolution. When provided, getPort() will only check availability on that specific host rather than all local addresses.

How It's Passed Through

The host option is passed through the call chain:

1. Into getPort(): You pass it as part of the options object:

   await getPort({port: 3000, host: '127.0.0.1'})
   

2. Through to getAvailablePort(): In [index.js:L61-L78], when you provide a host option, it gets passed directly to checkAvailablePort():

   if (options.host || options.port === 0) {
       return checkAvailablePort(options);
   }
   

3. To the server listener: In [index.js:L47-L60], the options (including host) are passed to server.listen():

   server.listen(options, () => {
       const {port} = server.address();
       // ...
   });
   

The host option is spread into netOptions [index.js:L122] and becomes part of the options passed to checkAvailablePort(), which ultimately passes it to Node's native server.listen() method.

When host is omitted, the library checks availability across all local addresses instead.

FOLLOW_UPS:

• What happens when host is omitted?
• How does ipv6Only option interact with host?
• Can I use IPv6 addresses with the host option?