dns_server.lua

shell.setPath(shell.path() .. ":/bin")
rednet.open("right")

print("DNS server started")

local dnsTable = {}


local function saveToFile(filename)
    local file = fs.open(filename, 'w')
    if file then
        file.write(textutils.serialize(dnsTable))
        file.close()
        print("DNS table saved to " .. filename)
    else
        print("Error: unable to open file for saving")
    end
end


local function loadFromFile(filename)
    if fs.exists(filename) then
        local file = fs.open(filename, 'r')
        if file then
            local content = file.readAll()
            dnsTable = textutils.unserialise(content) or {}
            file.close()
            print("DNS table loaded from " .. filename)
        else
            print("Error: Unable to open file for loading")
        end
    else
        print("No existing DNS table found, starting fresh")
    end
end


local function registerComputer(name, id)
    dnsTable[id] = name

    print("Registation successful")
    print("PC: " .. name .. " ID: " .. id)

    saveToFile("dns_table.txt")

    return true
end


local function getAllComputers()
    return dnsTable
end


loadFromFile("dns_table.txt")


while true do
    local senderID, message, protocol = rednet.receive()
    print("Something query")
    if type(message) == "string" then
        local data = textutils.unserialize(message)
        if protocol == "dns_register" then
            if data and data.name and data.id then
                registerComputer(data.name, data.id)
                rednet.send(senderID, "Registation has been successful", "dns_ack")
            end
        elseif protocol == "dns_list" then
            print("Protocol dns_list")
            local allComputers = getAllComputers()
            local listMessage = textutils.serialize(allComputers)
            rednet.send(senderID, listMessage, "dns_list_response")
        end
    elseif type(message) == "table" then
        if protocol == "log" then
            print("Protocol log")
            local file = fs.open("teleport.log", "a")

            if file then
                file.write(senderID .. ";" ..message.id .. ";" .. message.name .. "\n")
                file.close()
            else
                print("Something strange with file")
            end
        end
    else
        rednet.send(senderID, "something strange", "dns_list_response")
    end
end