dns_server.lua

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()
    if type(message) == "string" then
        local data = textutils.unserialize(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
        sleep(0,5)
    end
end