MC OpenComputers SS13 server status poller.

status.lua

-- I HAVE IMPORTED THE INTERWEB
local internet = require("internet")
local struct = require("struct")
local hex = require("hex")
local urlparse = require("urlparse")
local tprint = require("tprint")
local term = require("term")
local arg = {...}

function make_byond_request(address, port, message)
  -- Packet must always start with "?"
  if message:sub(1, 1) ~= "?" then
    message = "?" .. message
  end

  -- Build actual packet
  local packet = "\x00\x83"
  packet = packet .. struct.pack(">H", 6 + string.len(message))
  packet = packet .. "\x00\x00\x00\x00\x00"
  packet = packet .. message
  packet = packet .. "\x00"

  -- Write packet to BYOND server.
  local socket = internet.open(address, port)
  -- print(hex(packet))  
  socket:setTimeout(2)
  socket:write(packet)
  socket:flush()

  local error = nil
  local error_handler = function(e)
    error = e 
  end

  local read_response = function()
    if socket:read(2) ~= "\x00\x83" then
      error("Packet is not a valid BYOND response")
    end

    local packet_size = struct.unpack(">H", socket:read(2))
    local id_byte = socket:read(1)
    local received_packet = socket:read(packet_size-1)

    if id_byte == "\x2A" then
      -- Number, TODO
      error("Returning numbers is not supported yet")
    elseif id_byte == "\x06" then
      -- List!
      -- print(received_packet)
      response = urlparse(received_packet)
      -- tprint(response)
    else
      error("Unknown ID byte")
    end   
  end    

  local status = xpcall(read_response, error_handler)

  socket:close()
  
  if status then
    return response, nil
  else
    return nil, error
  end
end

URL = "baystation12.net"
port = 8000


if #arg == 2 then
  URL = arg[1]
  port = tonumber(arg[2])
end

while true do
  -- print("tock")
  local response, err = make_byond_request(URL, port, "?status")
  -- print("tick")
  term.clear()
  if err ~= nil then
    print("Unable to fetch status: "..err)
  else
    print("Player count: "..response.players)
    if response.active_players ~= nil then
      print("Active players: "..response.active_players)
    end
    if response.map_name ~= nil then
      print("Map: "..response.map_name)
    end
    if response.map ~= nil then
      print("Map: "..response.map)
    end 
    -- print("Revision: "..response.revision)
    -- print("Version: "..response.version)
  end
  os.sleep(5)
end