DNS Server by PrinzJuliano

local component = require("component")
local fs = component.filesystem
local io = require("io")
local modem = component.modem
local ser = require("serialization")

local dnsPort = 12
local fetchPort = 13
local dnsList = {}
local dnsPath = "/etc/dnsList.cfg"
if not fs.exists(dnsPath) then
  print("Creating DB")
  local crate = io.open(dnsPath, "w")
  crate:write("{}")
  crate:close()
end
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function cls()
  require("term").clear()
end

function showInfo()
  print("+----------------------------+")
  print("| DNS Server by PrinzJuliano |")
  print("+----------------------------+")
  print("Starting DNS Server on port: "..dnsPort)
  print("Reply channel is: "..fetchPort)
end

function readDB()
  local str = ""
  local file = io.open(dnsPath, "r")
  for line in file:lines() do
    str = str .. line
  end
  dnsList = ser.unserialize(str)
end

function addEntry(domain, addr, port)
  local crate = {}
  crate.addr = addr
  crate.port = port
  if dnsList[domain] == nil then
    dnsList[domain] = crate
    return true
  else
    return false
  end
end

function deleteEntry(domain)
  dnsList:remove(domain)
end

function writeDB()
  local file = io.open(dnsPath, "w")
  file:write(ser.serialize(dnsList))
  file:close()
end

showInfo()
readDB()
print("Add pjog once: " .. tostring(addEntry("pjog.de", "FICK DICH", -1)))
print("Add pjog twice: " .. tostring(addEntry("pjog.de", "hallo, ich bin der julian", 5)))

for k,v in pairs(dnsList) do
  print(k,v.addr, v.port)
end
writeDB()