whitelistReceive.lua

local modem = peripheral.wrap("top")
modem.open(1202)

function addToWhitelist (name)
    file = fs.open("whitelist.txt", "a")
    file.writeLine(name)
    file.close()
end

while true do
    local event, modemSide, senderChannel,
      replyChannel, message, senderDistance = os.pullEvent("modem_message")
    addToWhitelist(message)
end