Server

serverID = os.getComputerID()
modem = peripheral.wrap("back")
fs.delete("TimerKey.lua")
modem.open(2410)

term.clear()
term.setCursorPos(1,1)


function str2tbl (str)
    file = fs.open("temp.lua","w")
    file.write("return "..str)
    file.close()
    local data = dofile("temp.lua")
    fs.delete("temp.lua")
    return data
end

function findItemID (file, item, position)
    local data = dofile(file)
    for i = 1, table.maxn(data) do
        checkItem = str2tbl(data[i])
        if tostring(checkItem[position]) == tostring(item) then
            return i
        end
    end
    return nil
end

function returnTableItem (file, tbl, position)
    local data = dofile(file)
    checkTable = str2tbl(data[tbl])
    if tostring(checkTable[position]) then
        return checkTable
    else
        return nil
    end
end

function removeTableLine (file, position)
    itemID = findItemID("Users.lua", Username, 1)
    if itemID ~= nil then
        local tbl = dofile(file)
        table.remove(tbl, itemID)
        data = 'return {\n"'..table.concat(tbl,'",\n"')..'"\n}'
        fs.delete(file)
        file = fs.open(file,"a")
        file.write(data)
        file.close()
        return itemID
    else
        return nil
    end
end

function newTableLine (file, data)                                  -- Func 'newTableLine' expects the 'data' variable to be a string in the following format: "{ 'var1', 'var2', 'etc'}"
    if fs.exists(file) then
        local tbl = dofile(file)
    else
        tbl = {}
    end
    table.insert(tbl, (table.maxn(tbl) + 1), data)
    data = 'return {\n"'..table.concat(tbl,'",\n"')..'"\n}'
    fs.delete(file)
    file = fs.open(file,"a")
    file.write(data)
    file.close()
    return table.maxn(tbl)
end

function refreshTimer (channel,senderID,message)
    fileID = findItemID("TimerKey.lua", tostring(senderID), 1)
    if fileID ~= nil then
        savedID         = returnTableItem("TimerKey.lua", fileID, 1)
        savedChannel    = returnTableItem("TimerKey.lua", fileID, 2)
        savedKey        = returnTableItem("TimerKey.lua", fileID, 3)

        if senderID == savedID and channel == savedChannel and message[1] == savedKey then
            os.cancelTimer(key)
            removeTableLine("TimerKey.lua", fileID)
            newKey          = os.startTimer(10)
            secureChannel   = math.random(4096,65536)
            modem.open(secureChannel)
            modem.transmit(channel, secureChannel, newKey)
            if findItemID("TimerKey.lua", channel, 2) == nil then
                modem.close(channel)
            end
            newTableLine("TimerKey.lua","{'"..senderID.."','"..secureChannel.."','"..newKey.."'}")

        else
            modem.close(channel)
            removeTableLine("TimerKey.lua", fileID)
            modem.transmit(2410, senderID, -1)
            modem.transmit(2410, savedID, -1)
            modem.transmit(2410, savedChannel, -1)
            modem.transmit(2410, savedKey, -1)

        end
    end
end

while true do

    event, var1, var2, var3, var4, var5 = os.pullEventRaw()

    if event == "terminate" then
        print("Rebooting")
        RebootKey = os.startTimer(3)
        modem.transmit(2410,0,-1)

    elseif event == "modem_message" then
        side = var1; channel = var2; senderID = var3; message = var4; distance = var5
        if message == -1 then
            secureChannel = math.random(4096,65536)
            modem.open(secureChannel)
            newKey = os.startTimer(10)
            modem.transmit(2410, secureChannel, newKey)
            newTableLine("TimerKey.lua","{'"..senderID.."','"..secureChannel.."','"..newKey.."'}")

        else
            refreshTimer(channel,senderID,message)
        end

    elseif event == "timer" then
        key = var1
        if key == RebootKey then
            os.reboot()
        end

    elseif event == "key" then
        print(var1)
        if var1 == 211 then
            return
        end

    end
end