When disabling locking (mutexes) using: #define PJSUA_LOCK() #define PJSUA_TRY_LOCK() PJ_SUCCESS #define PJSUA_UNLOCK() #define PJSUA_LOCK_IS_LOCKED() PJ_TRUE i get a some kind of a lock when the connection is shutdown. No events will be thrown anymore and no connection can be reestablished anymore. Regards