possible web protocols in javascript
javascript, network-protocols, node.js
Solution
From Node.js, you can do pretty much anything. E.g. UDP is directly supported (dgram module which is shipped with node.js), and npm has a plethora of third-party modules for many other protocols, such as SMTP, IMAP, FTP and XMPP; see https://github.com/joyent/node/wiki/Modules for one list. And if you can't find a ready made module for your favorite protocol, you can implement one yourself.
Now when it comes to browsers, you are much more limited. Those you listed are all I know (browser plugins excluded, of course). So you'd need to connect to a proxy server with HTTP(S) or ws(s) and do the actual protocol stuff from there.
Problem
What are the alternatives to HTTP (per `XMLHttpRequest`) when establishing a server connection in JavaScript? The only one I know is the WebSocket protocol (per `WebSocket`). Their corresponding secure variants https and wss included. Would it be possible to choose an arbitrary protocol with JavaScript? How do you communicate with NTP, IMAP, UDP etc. -services for example in Node.js?