Inspecting websocket traffic with proxy

Found the answer myself in case anyone is interested (source is blogs.telerik.com)

WebSockets

Fiddler’s HTML5 WebSockets support continues to grow; Fiddler extensions can now capture and manipulate WebSocket messages by handling the FiddlerApplication.OnWebSocketMessage event.

In preparation for a full-featured WebSockets UI, Fiddler no longer spews WebSocket messages to the Log tab. If you’d like to re-enable that behavior until the full UI is available, you can do so using FiddlerScript. Simply click Rules > Customize Rules and add the following function inside your Handlers class.

static function OnWebSocketMessage(oMsg: WebSocketMessage) {

// Log Message to the LOG tab
FiddlerApplication.Log.LogString(oMsg.ToString());

/*
// Modify a message's content
var sPayload = oMsg.PayloadAsString();
if (sPayload.Contains("time")) {
    oMsg.SetPayload(sPayload + "... bazinga!");
}                            
*/
}