The IFrame and Websocket connection will both be based on the same Nonce. So, you will need to have the Nonce generated first.

After you have established a connection to the WebSocket, you will need to Register the Nonce.

ws.onopen = function() {        
        var obj = {
            "action":"REGISTER",
            "nonce":nonce
        };
        ws.send(JSON.stringify(obj));        
    };