Pasted

-- Furnace control
-- Setup:
-- (from above)
-- Comp - Outp
-- Inpu - Furn
-- the second computer under the furnace,
-- and a wired modem connecting the 2 computers
 
-- Computer 1: http://pastebin.com/06cjixf9
-- Computer 2: (this one) http://pastebin.com/RjyREdT2
 
-- Screenshots of setup:
-- 1 http://i.imgur.com/t9GFE2r.png
-- 2 http://i.imgur.com/WjnunBC.png
 
local furnace = peripheral.wrap("top")
or error("Unable to wrap furnace!",0)
 
local modemside = "bottom"
local modem
if peripheral.getType(modemside) == "modem" then
    modem = peripheral.wrap(modemside)
    or error("Unable to wrap modem!",0)
else error("No modem found, please correct!",0) end
 
local function getAllStacks(inv)
    local t = {}
    local size = inv.getInventorySize()
    for slot = 1,size do
        local item = inv.getStackInSlot(slot) or {}
        
        item.rawName = item.rawName or ""
        item.qty = item.qty or 0
        item.dmg = item.dmg or 0
        item.name = item.name or ""
        item.id = item.id or 0
        
        t[slot] = item
    end
    return t
end
 
local function isEmpty()
    local items = getAllStacks(furnace)
    for slot,item in pairs(items) do
        if item.qty > 0 then
            return false
        end
    end
    return true
end
 
modem.open(1)
print("Waits for control computer to ask if the furnace is empty.")
while true do
    local ev,p1,p2,p3,p4,p5 = os.pullEvent()
    
    if ev == "modem_message" and p1 == modemside and p2 == 1 then
        local msg = textutils.unserialize(p4)
        if type(msg) == "table" then
            if msg.task == "furnace"
            and msg.value == "question" then
                local reply = textutils.serialize({task="furnace",value=isEmpty()})
                modem.transmit(1,1,reply)
            end
        end
    end
end