startup

local modem = peripheral.wrap("left")
modem.open(3)
local event, modemSide, senderChannel,
  replyChannel, message, senderDistance = os.pullEvent("modem_message")

  print("I just received a message on channel: "..senderChannel)
  print("I should apparently reply on channel: "..replyChannel)
  print("The modem receiving this is located on my "..modemSide.." side")
  print("The message was: "..message)
  print("The sender is: "..(senderDistance or "an unknown number of").." blocks away from me.")