How to implement SIP Over Webscoket?

Question

SIP

There are several telephony providers Zadarma, SIPNET, Mango,
you need to implement the ability to call from a browser, the user himself will be able to choose which provider to call through, in the settings he will specify the connection data to the server (address, login, password).
Google gave the following tools to implement this (Freeswith, JSSIP), but it's not clear how to set it all up, FS is supposed to act as a proxy to the selected provider, implementing this via SIP over Websocket.
Please let me know if this is correct and how to set it up.

Answer 1

JSSIP is essentially a library. You need a "softphone" development only built into your web page. The so-called web background.
Just to take and install something - it will not work, the work of a web developer is required at least. And Google shows you FreeSwitch as one of the options for organizing WebRTC.