DNS check v1.0.0

local verze = "22.0223.R2"
local tArgs = { ... }
local idPC = os.getComputerID()
local RamCesta = ("/C/system/RAM/dns_check.tmp")

if fs.exists("/C/system/.core/defmodem") then
        local data = fs.open ("/C/system/.core/defmodem","r")
        modemPos = data.readLine()
        data.close()
        if not modemPos then
        modemPos = "offline"
        end
    else
        modemPos = "offline"
    end

if not (modemPos == "offline") then
    modem = peripheral.wrap(modemPos)
    modem.open(idPC)

    function zadat()
        term.write("DNSserver ID: ")
        srv_dns = tonumber(read())
        term.write("Domain: ")
        vyhledat(read())
        zadat()
    end

    function vyhledat(domain)
        modem.transmit(tonumber(srv_dns),53,idPC)
        modem.transmit(tonumber(srv_dns),54,domain)
        local a = prijmout()

        local data = fs.open(RamCesta, "w") data.writeLine(a) data.close()
        return a
    end

    function prijmout ()

    timerRX = os.startTimer(5)
        while true do
        local event,p1,p2,p3,p4 = os.pullEvent()
          if event == ("modem_message") then
                    if (p3 == 55) then
                        if p4 == false then
                        return false
                        else
                        return p4
                        end
                    end
          elseif event == "timer" then
            error("Connection timed out!")
            print()
            return
          end
        end
    end

    if #tArgs > 0 then
            if (tArgs[1] == "get") then
                srv_dns = tonumber (tArgs[2])
                local a = vyhledat(tArgs[3])
                if (tArgs[4] == "write") then print(a) end
                return a

            else
                term.setBackgroundColor(colors.blue)
                term.setTextColor(colors.yellow)
                term.clear()
                term.setCursorPos(1,1)
                zadat()
            end
    else
    zadat()
    end

else
    error("You must configure modem first")
end