Solution:
Tip requires full device control. If the virtual device does not respond correctly then an error will occur:
# tip tp1
tip: /dev/term/X1: not a tty
all ports busy
Ioland supports pushing the STREAMS module when used with an Iolan+ terminal server.
The -a switch must be used to enable STREAMS mode.
Trueport supports full I/O control when used with a Jetstream, or Lanstream server.
Trueport must be running in standard mode.