ng_tty problem

[Jerry Toung]

Hello List,
I want to monitor traffic on serial port /dev/cuaa0.
I am trying to build the following netgraph.

socket <---> tee node <---> tty node

I run ngctl manually with the error message below:

+ mkpeer . tee hook1 left
+ name .:hook1 mytee
+ mkpeer mytee: tty right hook
ngctl : send msg: Operation not permitted

Why is this?

Although kldstat -v shows ng_socket.ko, ng_tty.ko and ng_tee.ko

+ list command only shows socket and tee nodes.

What is the righ way of using ng_tty?

Thank you in advance.
Jerry