startup

p = peripheral.wrap("right") -- wrap modem
p.open(1) -- open
p.open(2) -- close
p.open(4) -- continue
while true do
  local event, modemSide, senderChannel, replyChannel = os.pullEvent("modem_message")
  if senderChannel == 1 then
    print("opening")
    turtle.digUp()
    turtle.suckUp()
    turtle.forward()
  end
  if senderChannel == 2 then
    print("closing")
    turtle.back()
    os.pullEvent("modem_message") -- pause for sync
    turtle.placeUp()
  end
end