oc_dns-client

local c = require "component"
local shell = require "shell"
local event = require "event"
local modem = c.modem
local fs = require "filesystem"

local path = "/etc/hosts"

local args = shell.parse(...)

local function usage()
  print("Usage:")
  print("    dns register <name>")
  print("    dns unregister")
  print("    dns update")
  return
end

if args[1] == "register" and args[2]
then
  modem.open(2)
  modem.broadcast(2, "dns_register", args[2])
  local _, to, from, port, dist, msg = event.pull(3, "modem_message")
  if port == 2 then
    if msg == "dns_addr_error" then
      print("Error: Address already registered.")
    elseif msg == "dns_name_error" then
      print("Error: Name already taken.")
    else
      print(to .. " registered as " .. args[2])
    end
  end
  modem.close(2)
elseif args[1] == "unregister" then
  modem.open(2)
  modem.broadcast(2, "dns_unregister")
  local _, to, from, port, dist, msg = event.pull(3, "modem_message")
  if port == 2 then
    if msg == "dns_unregister_error" then
      print("Error: You're not registered.")
    else
      print("Unregistered.")
    end
  end
  modem.close(2)
elseif args[1] == "update" then
  modem.open(2)
  modem.broadcast(2, "dns_update")
  local _, to, from, port, dist, msg = event.pull(3, "modem_message")
  if port == 2 then
    local file = io.open(path, "w")
    file:write(msg)
    io.close(file)
    if args[2] ~= "silently" then print("DNS Update done.") end
  end
  modem.close(2)
else
  usage()
end