[erlang-questions] stress test with tcp_server

[周敏]

Hi list,
   I am a newbie in erlang network program. I've wrote a simple stress test
case in erlang for testing how many connnetions can accepted by echo server
based on tcp_server.erl in one pc.
  below is  my test code:

-module(stress_test).

-export([start/0, tests/1]).

start() ->
    tests(12345).

tests(Port) ->
    io:format("starting~n"),
    spawn(fun() -> test(Port) end),
    spawn(fun() -> test(Port) end),
    spawn(fun() -> test(Port) end),
    spawn(fun() -> test(Port) end).

test(Port) ->
     case gen_tcp:connect("192.168.0.217", Port, [binary,{packet, 0}]) of
    {ok, _} ->
            test(Port);
    _ ->
        test(Port)
    end.

I've create four erlang processes to connect the echo server continuously.
the echo server code is like this:

-module(echo_server).
-export([start/0,stop/0]).

-define(LISTEN_PORT,12345).
-define(MAX_CONN, 5000).

start() ->
    process_flag(trap_exit, true),
    tcp_server:start_raw_server(?LISTEN_PORT,
                fun(Socket) -> socket_handler(Socket,self()) end,
                ?MAX_CONN,
                0).

socket_handler(Socket,Controller) ->
    receive
        {tcp, Socket, Bin} ->
            gen_tcp:send(Socket, Bin); % echo
        {tcp_closed, Socket} ->
            ok;
         _ ->
            socket_handler(Socket,Controller)
    end.

stop() ->
    tcp_server:stop(?LISTEN_PORT)


and to test how many connections the server can accept,  I've add only one
line in funtion possibly_start_another  of Joe's tcp_server.erl, like below:

possibly_start_another(false, Listen, Active, Fun, Max) ->
    case length(Active) of
    N when N < Max ->
        New = start_accept(Listen, Fun),
        io:format("current connetiones number is ~p~n",[N]),  % the  line  I
added to display connections number
        socket_loop(Listen, New, Active, Fun, Max);
    _ ->
        socket_loop(Listen, false, Active, Fun, Max)
    end

after compile these codes. It appears that only 1016 connections  can  be
accepted by the server.  What's matter with this?  I really  know what going
wrong .. thx at first.

Cheers,
Jeremy
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