From the example, adding .Raw to the transport is the only change you need to do in order to get it working - in comparsion to a regular socket setup (with channels) one would have. I assume you have this.
We have discussed changing the syntax here, but for now if you want to send data to the client you may do send socket_pid, {:binary, some_binary} or have this tuple returned on the handle callback - as shown in the example. Have a look here for a reference on op codes.
Would you mind sharing your code as well?
that does the trick!