udp_test.erl

-module(udp_test).
-export([start_server/0, client/1]).

start_server() ->
	spawn(fun() -> server(4000) end).

%% The server
server(Port) ->
	{ok, Socket} = gen_udp:open(Port, [binary]),
	io:format("server opened socket: ~p~n", [Socket]),
	loop(Socket).

loop(Socket) ->
	receive
		{udp, Socket, Host, Port, Bin} = Msg ->
			io:format("server received: ~p~n", [Msg]),
			N = binary_to_term(Bin),
			Fac = lib_misc:fac(N),
			gen_udp:send(Socket, Host, Port, term_to_binary(Fac)),
			loop(Socket)
	end.

%% The client
client(N) ->
	{ok, Socket} = gen_udp:open(0, [binary]),
	io:format("client opened socket = ~p~n", [Socket]),
	ok = gen_udp:send(Socket, "localhost", 4000, term_to_binary(N)),
	Value = receive
		{udp, Socket, _, _, Bin} = Msg ->
			io:format("client received: ~p~n", [Msg]),
			binary_to_term(Bin)
	after 2000 ->
		0
	end,
	gen_udp:close(Socket),
	Value.