Not a REST call: this is the WebSocket handshake. Connect to the URL below and the exchange answers 101 Switching Protocols; everything after that is frames, not requests.

Public: no key, no signature.

Carries no market data. Send {"Params":["ping"]} and the server answers {"Result":"pong"}.

The server also pings every 120 seconds on every channel, so an idle socket is kept alive without this.