server.lua

print("Starting remote database")
print("Loading database to memory... Please wait")
local db = {}
local function reloadFile()
if fs.exists("/.db") then
    local handler = fs.open("/.db","r")
    db = textutils.unserialise(handler.readAll())
    handler.close()
    print("Done loading")
else
    print("Database file non existent. Creating...")
    local handler = fs.open("/.db","w")
    handler.write(textutils.serialise({
    rdb = "1",
    rdbid = tostring(math.random(1,9999999)),
    keys = {}}))
    handler.close()
    error()
end
end
reloadFile()

print("Database version: " .. db.rdb)
local function checkKey(key)
    if db.keys[key] then
        return true
    else
        return false
    end
end
local function initialiseKey(key)
    if checkKey(key) then
        return false
    else
        db.keys[key] = {}
        return true
    end
end
local function checkBit(key,bit)
    if checkKey(key) then
        if db.keys[key][bit] then
            return true
        else
            return false
        end
    else
        return false
    end
end
local function readBit(key,bit)
    if checkBit(key,bit) then
        return true, db.keys[key][bit]
    else
        return false
    end
end
local function setBit(key,bit,value)
    if not checkKey(key) then
        initialiseKey(key)
    end
    if checkBit(key,bit) then
        db.keys[key][bit] = value
    else
        db.keys[key][bit] = value
    end
end

local function autosave()
while true do
    sleep(10)
    local handler = fs.open("/.db","w")
    handler.write(textutils.serialise(db))
    handler.close()
end
end
print("Server ID: " .. db.rdbid)
local function server()
    print("Booting server up")
    local modems = {peripheral.find("modem")}
    for k,v in pairs(modems) do
        v.open(410)
    end
    while true do
        local v = {os.pullEvent("modem_message")}
        if v[3] == 410 and v[4] == 410 then
         if v[5].serverId == db.rdbid then
             print("Server id: " .. db.rdbid)
             local response = {}
             response.messageid = v[5].messageId
             response.content = {}
             if v[5].type == "exists-key" then
                 response.content = checkKey(v[5].content)
             elseif v[5].type == "exists-bit" then
                 response.content = checkBit(v[5].content.key,v[5].content.bit)
             elseif v[5].type == "get" then
                 local exists, value = readBit(v[5].content.key,v[5].content.bit)
                 response.content.exists = exists
                 response.content.value = value or false
             elseif v[5].type == "set" then
                 setBit(v[5].content.key,v[5].content.bit,v[5].content.value)
                 response.content = true
             else
                 print("Unrecognised type. Do the versions match?")
             end
             local modems = {peripheral.find("modem")}
             for k,v in pairs(modems) do
                 v.transmit(410,410,response)
             end
         else
          print("Got request, however it was ignored because it wasnt targeted to me")
         end
        end
    end
end
parallel.waitForAny(server,autosave)