redNetMonitor

-- Finds devices connected to the computer, wraps them
local function getDevices(deviceType) -- This function was taken from https://github.com/sandalle/minecraft_bigreactor_control and has been modified by https://github.com/Sanwi
	local deviceName = nil
	local deviceIndex = 1
	local deviceList, deviceNames = {}, {} -- Empty array, which grows as we need
	local peripheralList = peripheral.getNames() -- Get table of connected peripherals
	for peripheralIndex = 1, #peripheralList do -- Log every device found
		if (string.lower(peripheral.getType(peripheralList[peripheralIndex])) == deviceType) then -- Log devices found which match deviceType and which device index we give them
			deviceNames[deviceIndex] = peripheralList[peripheralIndex]
			deviceList[deviceIndex] = peripheral.wrap(peripheralList[peripheralIndex])
			deviceIndex = deviceIndex + 1
		end
	end -- for peripheralIndex = 1, #peripheralList do
	return deviceList, deviceNames
end

local deviceList, deviceNames = getDevices("modem")
local modem = deviceList[1]

rednet.open(deviceNames[1])

while true do
  local senderId, message, protocol = rednet.receive()

  if type(message) == "string" then
    print(message)
  elseif type(message) == "table" then
    print(textutils.serialize(message))
  else
    print(message)
  end
  local event,key = os.pullEvent("key")
end