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# `resolve-alpn`
[](https://github.com/szmarczak/resolve-alpn/actions)
[](https://codecov.io/gh/szmarczak/resolve-alpn)
## API
### resolveALPN(options, connect = tls.connect)
Returns an object with an `alpnProtocol` property. The `socket` property may be also present.
```js
const result = await resolveALPN({
host: 'nghttp2.org',
port: 443,
ALPNProtocols: ['h2', 'http/1.1'],
servername: 'nghttp2.org'
});
console.log(result); // {alpnProtocol: 'h2'}
```
**Note:** While the `servername` option is not required in this case, many other servers do. It's best practice to set it anyway.
**Note:** If the socket times out, the promise will resolve and `result.timeout` will be set to `true`.
#### options
Same as [TLS options](https://nodejs.org/api/tls.html#tls_tls_connect_options_callback).
##### options.resolveSocket
By default, the socket gets destroyed and the promise resolves.<br>
If you set this to true, it will return the socket in a `socket` property.
```js
const result = await resolveALPN({
host: 'nghttp2.org',
port: 443,
ALPNProtocols: ['h2', 'http/1.1'],
servername: 'nghttp2.org',
resolveSocket: true
});
console.log(result); // {alpnProtocol: 'h2', socket: tls.TLSSocket}
// Remember to destroy the socket if you don't use it!
result.socket.destroy();
```
#### connect
Type: `Function<TLSSocket> | AsyncFunction<TLSSocket>`\
Default: [`tls.connect`](https://nodejs.org/dist/latest-v16.x/docs/api/tls.html#tls_tls_connect_options_callback)
**Note:** No matter which function is used (synchronous or asynchronous), it **must** accept a `callback` function as a second argument. The `callback` function gets executed when the socket has successfully connected.
## License
MIT
|
