FTP.lua

local component = require("component")
local event = require("event")
local modem = component.modem
local keyboard = require("keyboard")
local DNSAddress = "9955471e-b28f-4001-9d66-79c28c75be2d"
local homePath = "/home/"
local messageArray = {}
local brokenMessageArray = {}
local maxSize

local port = 21
local timeout = 5

function OpenModem(port)
  modem.open(port)
  if modem.isOpen(port) then
    print("Successfully opened port " .. port)
  else
    print("Could not open port " .. port .. ", closing server")
  end
end

function Quit()
  modem.close(21)
  if modem.isOpen(21) == false then
    print("Successfully closed port 21, closing program...")
  else
    print("Could not close port 21, please contact admin.")
  end
  os.exit()
end

function EventPull(timeout)
  for i=1,10 do
    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 DNS on port " .. port)
      --return pullArray
    end
    if pullArray[1] ~= nil then
      return pullArray
    end
    i = i + 1
  end
end

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 = {}
  while true do
    modem.send(remoteAddress, port, message)
    timeoutPull = EventPull(timeout)
    if timeoutPull[1] ~= nil then
      break
    end
  end
end

local function OpenFile(fileName)
  local path = homePath .. fileName
  local file = io.open(path, "r")
  local fileSize, _ = file:seek("end")
  file:seek("set")
  fileString = file:read(fileSize)
  file:close()
  return fileString
end

local function PacketBreak(inputString)
  local tempArray = {}
  tempArray[3] = "This is to stop stupid LUA errors"
  maxSize = (modem.maxPacketSize()) - 2 --subtraction of 2 is to account for overhead of message
  stringLength = string.len(inputString)
  if stringLength > maxSize then
    print("File is too long, splitting into multiple files...")
    stringOne = string.sub(inputString, 1, math.floor(stringLength/2))
    stringTwo = string.sub(inputString, (math.floor(stringLength/2)) + 1, stringLength)
    tempArray[1] = stringOne
    tempArray[2] = stringTwo
  end
  return tempArray
end

local args = {...} --send/recieve, who to send to, filename
if args[1] == nil then error("Provide function of the program (send/recieve).") end
if args[2] == nil then error("Provide who you are sending this file to or receive from.") end

OpenModem(port)
if args[1] == "send" then
  if args[3] == nil then error("Provide the file name.") end
  print("Preparing to send file...")
  local sendString = OpenFile(args[3])
  if sendString == nil then
    print("The target file is empty. Choose another.")
    Quit()
  end
  brokenMessageArray = PacketBreak(sendString)
  if brokenMessageArray[1] == nil then
    SendTimeout(OpenFile(args[2]), port, sendString, timeout)
    print("File sent to " .. args[2] .. " over port " .. port)
    SendTimeout(OpenFile(args[2]), port, "DONE", timeout)
  else
    for i, loopString in ipairs(brokenMessageArray) do
      SendTimeout(OpenFile(args[2]), port, loopString, timeout)
    end
    SendTimeout(OpenFile(args[2]), port, "DONE", timeout)
  end
elseif args[1] == "receive" then
  if args[3] == nil then error("Provide a name for the file.") end
  print("Preparing to receive file at path " .. args[3])
  messageArray = EventPull(timeout)
  SendACK(messageArray[2], messageArray[3])
  local receivedFile = io.open(homePath .. args[3], "w")
  receivedFile:write(messageArray[5])
  receivedFile:flush()
  receivedFile:close()
  local finished = false
  while finished == false do
    messageArray = EventPull(timeout)
    SendACK(messageArray[2], messageArray[3])
    if messageArray[5] == "DONE" then
      finished = true
    else
      local receivedFile = io.open(homePath .. args[3], "a")
      receivedFile:write(messageArray[5])
      receivedFile:flush()
      receivedFile:close()
    end
  end
  print("File " .. args[3] .. " has been saved with the path " .. homePath .. args[3])
end
Quit()