websocketClientPrepareHandshake

void websocketClientPrepareHandshake(soup.message.Message msg,  string origin =  null,  string[]  protocols =  null,  gobject.type_class.TypeClass[]  supportedExtensions =  null)

Adds the necessary headers to msg to request a WebSocket handshake including supported WebSocket extensions.

The message body and non-WebSocket-related headers are not modified.

This is a low-level function; if you use [soup.session.Session.websocketConnectAsync] to create a WebSocket connection, it will call this for you.

Parameters

`msg`	a #SoupMessage
`origin`	the "Origin" header to set
`protocols`	list of protocols to offer
`supportedExtensions`	list of supported extension types