@agramfort Take a look at these methods. In the real client they're used to register / unregister callbacks and prepare reality to join in. Our data acquistion mechnism for testing is much more primitive, it's only a raw file. So we don't need those guys. We only need them to make the RtEpochs object happy, but they don't need to do anythin because we don't have threads and we already have the data. good?