RNP v1A

port=8000
modem={}
name=os.getComputerID()

--broadcasts go in form: type, src, dest, step (array of hop names), data

function openModems()
  n=1
  if peripheral.getType("back")=="modem" then modem[n]=peripheral.wrap("back") n=n+1 end
  if peripheral.getType("top")=="modem" then modem[n]=peripheral.wrap("top") n=n+1 end
  if peripheral.getType("left")=="modem" then modem[n]=peripheral.wrap("left") n=n+1 end
  if peripheral.getType("right")=="modem" then modem[n]=peripheral.wrap("right") n=n+1 end
  for i=1, #modem do
    modem[i].open(port)
  end
end

function broadcast(type, src, dest, dat) --takes type, src, dest, dat
  local packet={}
  packet.type=type
  packet.src=src
  packet.dest=dest
  step={}
  step[1]=name
  packet.step=textutils.serialize(step)
  packet.dat=textutils.serialize(dat)
  local transmit=textutils.serialize(packet)
  for i=1, #modem do
    modem[i].transmit(port, port, transmit)
  end
  openModems()
end

function receive(type) --returns type, src, dest, step, dat
  local event, mSide, sChannel, rChannel, msg, senderDist = os.pullEvent("modem_message")
  openModems()
  local packet=textutils.unserialize(msg)
  if packet.type==type or type==nil or type==false or type==0 then
    if packet.dest==nil or packet.dest==name then
      return packet.type, packet.src, packet.dest, textutils.unserialize(packet.step), textutils.unserialize(packet.dat)
    end
  end
  return nil
end

function setName(n)
  name=n
end

function start()
  openModems()
  name=os.getComputerID()
end