The nng_pipe_listener()
function returns the nng_listener
that created the pipe p.
If the pipe was not created by a listener, then the returned value will
have an identifier (nng_listener_id()
) of -1
.
This function returns the listener that created the pipe, unless it was
not created by a listener, in which case a value initialized with
NNG_LISTENER_INITIALIZER
will be returned.