Shared UDP socket gen_server

udp_test.erl

-module(udp_test).
-behaviour(gen_server).
-define(SERVER, ?MODULE).
-define(PORT, 9876).
-define(TIMEOUT, 10).

%% ------------------------------------------------------------------
%% API Function Exports
%% ------------------------------------------------------------------

-export([start_link/2, send/1,
         test_stuff/0, start_stuff/1]).

%% ------------------------------------------------------------------
%% gen_server Function Exports
%% ------------------------------------------------------------------

-export([init/1, handle_call/3, handle_cast/2, 
         handle_info/2, terminate/2, code_change/3]).

-record(state, {id = 0,
                sock}).

%% ------------------------------------------------------------------
%% API Function Definitions
%% ------------------------------------------------------------------

start_link(ID, Sock) ->
  gen_server:start_link(?MODULE, [{id, ID}, {socket, Sock}], []).

%% ------------------------------------------------------------------
%% gen_server Function Definitions
%% ------------------------------------------------------------------

init(Args) ->
  ID = proplists:get_value(id, Args, 1),
  case proplists:get_value(socket, Args) of
    undefined -> 
      {stop, nosock};
    Sock -> 
      {ok, #state{ id=ID, sock=Sock }, 0}
  end.

handle_call(_Request, _From, State) ->
  {stop, {error, unknownmsg}, State}.

handle_cast(_Request, State) ->
  {stop, {error, unknownmsg}, State}.

handle_info(timeout, #state{ sock=undefined } = State) ->
  {noreply, State, ?TIMEOUT};
handle_info(timeout, #state{ id=ID, sock=Sock } = State) ->
  TO = case gen_udp:recv(Sock, 4) of
    {error, _} -> ?TIMEOUT;
    _Data ->
      catch ets:insert_new(?MODULE, {ID, 0}),
      catch ets:update_counter(?MODULE, ID, 1),
      ?TIMEOUT
  end,
  {noreply, State, TO}.

terminate(_Reason, _State) ->
  ok.

code_change(_OldVsn, State, _Extra) ->
  {ok, State}.

%% ------------------------------------------------------------------
%% Test Function Definitions
%% ------------------------------------------------------------------

test_stuff() -> 
  start_stuff(10), 
  [udp_test:send("fooobaar") || _ <- lists:seq(1,1000)],
  timer:sleep(1000),
  io:format("Total: ~p~n", [ets:tab2list(?MODULE)]),
  init:stop().

start_stuff(N) -> 
  ets:new(?MODULE, [named_table, public]),
  {ok, S} = gen_udp:open(?PORT, [{active, false}, binary]),
  [start_link(ID, S) || ID <- lists:seq(1, N)].

send(Data) ->
  spawn(fun() ->
        {ok, S} = gen_udp:open(0, [{active, false}, binary]),
        gen_udp:send(S, localhost,?PORT, Data)
    end).