DNSProgram.lua

local component = require("component")
local event = require("event")
local fs = require("filesystem")
local modem = component.modem
local keyboard = require("keyboard")
local addressFile
local addressFileString
local addressFilePath = "/home/AddressDirectory"
local addressDirectoryPath = "/home/Addresses/"
local modemStrength
local requestedGUID
local wireless = true
local timeOut = 15
local chosenPort = 42
local addComputerPort = 50
local retrieveGUIDPort = 60

local function IsWireless(wireless)
  local signal
  if wireless then
    signal = 5000
  else
    signal = 0
  end
  return signal
end

local function OpenModem(modemStrength, addComputerPort, retrieveGUIDPort, oldPort)
  modem.open(addComputerPort)
  modem.open(retrieveGUIDPort)
  modem.open(oldPort)
  modemStrength = IsWireless(wireless)
  modem.setStrength(modemStrength)
  print("Wireless modem strength has been set to " .. modemStrength)
  if modem.isOpen(oldPort) and modem.isOpen(addComputerPort) and modem.isOpen(retrieveGUIDPort) then
    print("Successfully opened ports.")
  else
    print("Could not open ports, exiting program...")
    os.exit()
  end
end

local function Quit() --need to add variables to this and not be a scrub and use numbers
  print("Closing ports.")
  modem.close(42)
  modem.close(50)
  modem.close(60)
  if modem.isOpen(50) == false and modem.isOpen(60) == false and modem.isOpen(42) == false then
    print("Successfully closed ports, shutting down server...")
    os.exit()
  else
    print("Ports could not close, contact admin to resolve security hole.")
    os.exit()
  end
end

local function OpenFile(addressFilePath)
  if fs.exists(addressFilePath) ~= true then
    addressFile = io.open(addressFilePath, "w")
    addressFile:close()
    print("DNS file not found, generating a new one.")
  end
  addressFile = io.open(addressFilePath, "r")
  fileSize, _ = addressFile:seek("end")
  addressFile:seek("set")
  addressFileString = addressFile:read(fileSize)
  if addressFileString == nil then
    addressFileString = ""
  end
  print("Address file string is " .. addressFileString)
  addressFile:close()
  print("Server address file loaded.")
end

local function SaveToFile(text, addressFilePath)
  newAddressFile = io.open(addressFilePath, "w")
  newAddressFile:write(text)
  newAddressFile:close()
end

local function CreateFile(fileName, filePath, GUID)
  file = io.open(filePath .. fileName, "w")
  file:write(GUID)
  file:close()
  print("New GUID file has been created with the filepath " .. filePath .. fileName)
end

local function RemoveDashes(guid)
  return guid:sub(1, 8) .. guid:sub(10, 13) .. guid:sub(15, 18) .. guid:sub(20, 23) .. guid:sub(25, 38)
end

local function AddDashes(guid)
  return guid:sub(1, 8) .. "-" .. guid:sub(9, 12) .. "-" .. guid:sub(13, 16) .. "-" .. guid:sub(17, 20) .. "-" .. guid:sub(21, 34)
end

local function EventPull(timeOut)
  local type, _, foreignAddress, port, distance, message = event.pull(timeOut)
  local pullArray = {}
  if type == "key_down" then
    if keyboard.isAltDown() then
      Quit()
    end
  elseif type == "modem_message" then
    pullArray[1] = type
    pullArray[2] = foreignAddress
    pullArray[3] = port
    pullArray[4] = distance
    pullArray[5] = message
    print("Message has been received from " .. pullArray[2] .. " on port " .. pullArray[3])
  end
  return pullArray
end

local function SendACK(remoteAddress, port)
  modem.send(remoteAddress, port, "ACK")
  print("ACK has been sent to " .. remoteAddress .. " on port " .. port)
end

local function SendTimeout(remoteAddress, port, message, timeOut)
  local timeoutPull = {}
  loopActive = true
  while loopActive do
    modem.send(remoteAddress, port, message)
    timeoutPull = EventPull(timeOut)
    if timeoutPull[1] ~= nil then
      loopActive = false
    end
  end
end

local function AddComputer(remoteAddress, port, addressFileString, addressFilePath, GUIDFilePath, computerName)
  SendACK(remoteAddress, port)
  addressFileString = addressFileString .. "\n" .. RemoveDashes(remoteAddress) .. " = " .. computerName
  SaveToFile(addressFileString, addressFilePath)
  print("Remote address: " .. remoteAddress .. " has been added under the name " .. computerName .. ".")
  local storedFormat = RemoveDashes(remoteAddress)
  CreateFile(computerName, GUIDFilePath, storedFormat)
end

local function RetrieveGUID(name, directoryPath)
  local path = directoryPath .. name
  if fs.exists(path) then
    local file = io.open(path, "r")
    local fileSize, _ = file:seek("end")
    file:seek("set")
    local fileContents = file:read(fileSize)
    file:close()
    return fileContents
  else
    return "fail"
  end
end

local function DataRead() --method is deprecated
  local continue = true
  while continue do
    local type, _, remoteAddress, port, _, message = event.pull()
    if type == "key_down" then
      continue = false
    elseif type == "modem_message" and port == 42 then
      print(message)
    end
  end
end

OpenModem(modemStrength, addComputerPort, retrieveGUIDPort, chosenPort)
print("Press ALT to exit")
OpenFile(addressFilePath)
while true do
  local firstArray = EventPull(timeout)
  if firstArray[3] == retrieveGUIDPort then
    isMatching = addressFileString:match(RemoveDashes(firstArray[2]))
    if isMatching then
      SendACK(firstArray[2], firstArray[3])
      requestedGUID = RetrieveGUID(firstArray[5], addressDirectoryPath)
      if requestedGUID ~= "fail" then
        SendTimeout(firstArray[2], firstArray[3], AddDashes(requestedGUID), timeOut)
        print("GUID: " .. AddDashes(requestedGUID) .. " has been sent to " .. firstArray[2])
      else
        SendTimeout(firstArray[2], firstArray[3], "500", timeOut)
        print(firstArray[2] .. " attempted to query file " .. firstArray[5] .. ", which does not exist.")
      end
    end
  elseif firstArray[3] == addComputerPort then
    AddComputer(firstArray[2], firstArray[3], addressFileString, addressFilePath, addressDirectoryPath, firstArray[5])
    OpenFile(addressFilePath)
  else
    if firstArray[1] == "modem_message" then
      modem.send(firstArray[2], firstArray[3], "DNS does not recognize this port.")
      print("Receieved unauthorized request from " .. firstArray[2])
    end
  end
end