There is an atlassian-synchrony-proxy.log :
2018-03-27 11:43:00 DEBUG SynchronyDispatcherServletInitializer:66 - No ContextLoaderListener registered, as createRootApplicationContext() did not return an application context
2018-03-27 11:43:01 DEBUG WebSocketConfig:34 - synchronySockjsClientLib=/synchrony-proxy/resources/js/vendor/sockjs.min.js