function detectModem()
  for _,side in ipairs(rs.getSides()) do
    if peripheral.isPresent(side) then
      if peripheral.getType(side) == "modem" then
        rednet.open(side) 
        return side
      end
    end
  end
  return false
end

local modem = detectModem()
local event,param1,param2,param3
local x,y = 0,0
if modem == false then
  print("No modem found!")
else
  rednet.open(modem)
end
term.clear()
term.setCursorPos(1,2)

while true do
  x,y = term.getCursorPos()
  term.setCursorPos(1,1)
  write("Press [SPACE] key to stop!")
  term.setCursorPos(x,y)
  event, param1, param2, param3 = os.pullEvent()
  if event == "rednet_message" then
    print("Rednet message: "..param2)
  elseif event == "key" and param1 == 57 then
    break
  end
end

rednet.close(modem)