if component == nil then
  component = require("component")
end

local function proxy(name, required)
  local address = component and component.list(name)()
  if not address and required then
    error("Missing component '" .. name .. "'")
  end
  return address and component.proxy(address) or nil
end

local modem = proxy("modem", true)
modem.open(1)
modem.setStrength(500)

local robot = proxy("robot", true)

while true do
  local signal, _, remoteAddress, port, distance, payload = computer.pullSignal()

  if signal == "modem_message" then
    if payload == "ping" then
      computer.beep()
      modem.send(remoteAddress, port, "pong", robot.name())
    else
      pcall(load(payload))
    end
  end
end