dns_server.lua

rednet.open("right")

print("DNS server started")

local dnsTable = {}


local function saveToFile(fulename)
    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 loadlFromFile(filename)
    if fs.exists(filename) then
        local file = fs.open(fileopen, '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)
    if dnsTable[name] then
        print("Registration failed: Name already registred")
        return false
    end

    dnsTable[name] = id
    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()
    local data = textutils.unserialise(message)

    if protocol == "dns_register" then
        if data and data.name and data.id then
            if registerComputer(data.name, data.id) then
                rednet.send(senderID, "Registation has been successful", "dns_ack")
            else
                rednet.send(senderID, "Registration failed: Name already registered", "dns_ack")
            end
        end
    elseif protocol == "dns_list" then
        local allComputers = getAllComputers()
        local listMessage = textutils.serialize(allComputers)
        rednet.send(senderID, listMessage, "dns_list_response")
    end
end