/// <summary>
        ///
        /// </summary>
        /// <returns></returns>
        private int start()
        {
            int status = -1;

            // prepare configuration struct
            // read data from Config interface. If null read all values directly from SipConfigMore
            if (!Config.IsNull)
            {
                ConfigMore.listenPort = Config.SIPPort;
            }

            PjsipMethods.dll_setSipConfig(ConfigMore);
            status = PjsipMethods.dll_init();

            if (status != 0)
            {
                return(status);
            }

            status |= PjsipMethods.dll_main();

            return(status);
        }