adds logging server

centralLoggingSystem/readme.md

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+# central logging system
+Logs data sent to it by various computers and prints it on printed pieces of paper.
+
+# Server Setup
+1. Download `server.lua` and put it on your computer (for example with wget) and put it in the startup folder (you might have to make this).
+2. Attach a printer and a modem to the computer and note on what side of the computer they are.
+3. Edit the file and change the variables `printerSide` and `modemSide` if needed.
+4. Download the dependency and "install" it by putting `AES.lua` in the same directory as the program.
+5. Decide on a shared key, this has to be a number (for example use something like `openssl rand -hex 16` and prefix it with `0x` to get a random 16 byte number)
+6. Run `set AES.key <your shared key>`
+7. Choose a channel number and set the channel by changing the `channel` variable.
+
+# Client Setup
+
+# Dependencies
+- [Lua_AES](https://github.com/idiomic/Lua_AES)
+

centralLoggingSystem/server.lua

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+settings.define("AES.key", {
+    description = "AES key used for encryption",
+    type = number
+})
+
+local printerSide = "right"
+local modemSide = "top"
+
+local channel = 59598
+
+local AES = require("/AES")
+local key = settings.get("AES.key") or error("No AES Key set")
+
+local modem = peripheral.wrap(modemSide) or error("No modem found")
+modem.closeAll()
+modem.open(channel)
+
+local printer = peripheral.wrap(printerSide) or error("No printer found")
+
+function startPage()
+    if not printer.newPage() then
+        error("cant start new page")
+    end
+    printer.setPageTitle(os.date())
+end
+
+local pageOpened = false
+function printNewLog(line)
+    print(line)
+    if not pageOpened then
+        startPage()
+        pageOpened = true
+    end
+    local width, height = printer.getPageSize()
+    local currX, currY = printer.getCursorPos()
+
+    local neededLines = math.ceil(#line / width)
+    if neededLines > height+1 - currY then -- +1 because being on the last line still leaves one free
+        startPage()
+    end
+    local i = 1
+    while i <= #line do
+        printer.write(line:sub(i, i + width-1))
+        i = i + width - 1
+        printer.setCursorPos(1, currY+1)
+        currX, currY = printer.getCursorPos()
+    end
+    if currY == height then
+        printer.endPage()
+        pageOpened = false
+    end
+end
+
+
+local modemMessage = {}
+local decrypted = nil
+local obj = nil
+while true do
+    modemMessage = {os.pullEvent("modem_message")}
+    decrypted = AES.ECB_256(AES.decrypt, key, modemMessage[5])
+    obj = textutils.unserialise(decrypted)
+    if obj then
+        if obj.sender and obj.message then
+            printNewLog(string.format("%s %s: %s", os.date(), obj.sender, obj.message))
+        else
+            print("invalid object received")
+            print(decrypted)
+        end
+    else
+        print("invalid object received")
+    end
+end