If you have error to establish connection with socket, add this code in nginx .config file.

		if ($http_origin ~* (https?://[^/]*\.example\.com(:[0-9]+)?)$) {
            set $cors "true";
        }

        if ($request_method = 'OPTIONS') {
            set $cors "${cors}options";
        }

        if ($request_method = 'GET') {
            set $cors "${cors}get";
        }
        if ($request_method = 'POST') {
            set $cors "${cors}post";
        }

        if ($cors = "trueget") {
            add_header 'Access-Control-Allow-Origin' "$http_origin";
            add_header 'Access-Control-Allow-Credentials' 'true';
        }

        if ($cors = "truepost") {
            add_header 'Access-Control-Allow-Origin' "$http_origin";
            add_header 'Access-Control-Allow-Credentials' 'true';
        }

        if ($cors = "trueoptions") {
            add_header 'Access-Control-Allow-Origin' "$http_origin";
            add_header 'Access-Control-Allow-Credentials' 'true';
            add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
            add_header 'Access-Control-Allow-Headers' 'Authorization,Content-Type,Accept,Origin,User-Agent,DNT,Cache-Control,X-Mx-ReqToken,Keep-Alive,X-Requested-With,If-Modified-Since';
            add_header 'Content-Length' 0;
            add_header 'Content-Type' 'text/plain charset=UTF-8';
            return 204;
        }