Feature request: Available port for any localhost host (localhost, 0.0.0.0, 127.0.0.1)

[dylang]

If server.listen is used with a host, then get-port only returns the correct result if the same host value is provided.

// Some other project running on your machine:
server.listen(3000, 'localhost', cb);

This works, because we put in the host localhost, matching above:

// Your project:
await getPort({ port: 3000, host: 'localhost' }) 
// => Random port that is not bound to localhost, good!

However, when you don't know what host was used in the other project, or what host will be used in yours, you could be in trouble:

// Some other project running on your machine:
server.listen(3000, 'localhost', cb);

// Your project does one of these:

await getPort({ port: 3000 }) 
// => 3000...

await getPort({ port: 3000, host: '0.0.0.0' }) 
// => 3000...

await getPort({ port: 3000, host: '127.0.0.1' }) 
// => 3000...

await getPort({ port: 3000, host: '::' }) 
// => 3000...

If that 3000 port is then used later in your code with localhost, it will fail.

This might be a deficiency or feature in libev, or I'm not understanding how port binding works when the host is provided.

Workaround 1

Always use the same host when creating your server as used when running get-port. I'm finding that to not always be feasible.

Workaround 2

Math.max(
  await getPort({ port: 3000, host: 'localhost' }),
  await getPort({ port: 3000, host: '0.0.0.0' })
);
// => Will always be a random port, even if 3000 is available, 
// because `lockedPorts` ignores the `host`, so one of the two 
// getPort calls will think 3000 is already locked and return a random port.

Potential solution?

Maybe a possible workaround is to allow for passing in an array of hosts, or an option to check all localhost variants?

[sindresorhus]

See my comment in #31 (comment). I think it indeed should just work by default.