What is resolve-alpn?
The resolve-alpn npm package is designed to help Node.js applications determine the Application-Layer Protocol Negotiation (ALPN) protocol that a server supports. ALPN is a TLS extension used for negotiating which protocol should be performed over a secure connection. This is particularly useful for applications that need to decide between different protocols like HTTP/2 or HTTP/1.1 when connecting to a server.
What are resolve-alpn's main functionalities?
Determining ALPN protocol
This feature allows developers to programmatically determine the ALPN protocol supported by a server. The code sample demonstrates how to use the resolve-alpn package to check which ALPN protocol ('http/1.1', 'h2', etc.) a server supports by specifying the host and port.
const resolveAlpn = require('resolve-alpn');
resolveAlpn({
host: 'example.com',
port: 443
}).then((negotiatedProtocol) => {
console.log(negotiatedProtocol);
}).catch((error) => {
console.error(error);
});
Other packages similar to resolve-alpn
http2-wrapper
While not exclusively focused on ALPN negotiation, http2-wrapper includes functionality for automatically negotiating HTTP/2 connections using ALPN. It provides a higher-level API for making HTTP requests over either HTTP/1.1 or HTTP/2, depending on server support. This makes it a more comprehensive solution for HTTP communication compared to resolve-alpn, which is more narrowly focused on the ALPN negotiation process.
resolve-alpn
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API
resolveALPN(options)
Returns an object with an alpnProtocol
property. The socket
property may be also present.
const result = await resolveALPN({
host: 'nghttp2.org',
ALPNProtocols: ['h2', 'http/1.1']
});
console.log(result);
options
Same as TLS options.
options.resolveSocket
By default, the socket gets destroyed and the promise resolves.
If you set this to true, it will return the socket in a socket
property.
const result = await resolveALPN({
host: 'nghttp2.org',
ALPNProtocols: ['h2', 'http/1.1'],
resolveSocket: true
});
console.log(result);
result.socket.end();
License
MIT